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2. Commands

This section lists the commands acceptable to `gnuplot` in alphabetical order. Printed versions of this document contain all commands; on-line versions may not be complete. Indeed, on some systems there may be no commands at all listed under this heading.

Note that in most cases unambiguous abbreviations for command names and their options are permissible, i.e., "`p f(x) w li`" instead of "`plot f(x) with lines`".

In the syntax descriptions, braces ({}) denote optional arguments and a vertical bar (|) separates mutually exclusive choices.


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2.1 cd

The cd command changes the working directory.

Syntax:

 
      cd '<directory-name>'

The directory name must be enclosed in quotes.

Examples:

 
      cd 'subdir'
      cd ".."

It is recommended for DOS and Windows users to use single-quotes--backslash [\] has special significance inside double-quotes and has to be escaped. For example,

 
      cd "c:\newdata"

fails, but

 
      cd 'c:\newdata'
      cd "c:\\newdata"

works as expected.


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2.2 call

The call command is identical to the load command with one exception: you can have up to ten additional parameters to the command (delimited according to the standard parser rules) which can be substituted into the lines read from the file. As each line is read from the called input file, it is scanned for the sequence `$` (dollar-sign) followed by a digit (0-9). If found, the sequence is replaced by the corresponding parameter from the call command line. If the parameter was specified as a string in the call line, it is substituted without its enclosing quotes. Sequence `$#` is replaced by the number of passed parameters. `$` followed by any character will be that character; e.g. use `$$` to get a single `$`. Providing more than ten parameters on the call command line will cause an error. A parameter that was not provided substitutes as nothing. Files being called may themselves contain call or `load` commands.

The call command _must_ be the last command on a multi-command line.

Syntax:

 
      call "<input-file>" <parameter-0> <parm-1> ... <parm-9>

The name of the input file must be enclosed in quotes, and it is recommended that parameters are similarly enclosed in quotes (future versions of gnuplot may treat quoted and unquoted arguments differently).

Example:

If the file 'calltest.gp' contains the line:

 
      print "argc=$# p0=$0 p1=$1 p2=$2 p3=$3 p4=$4 p5=$5 p6=$6 p7=x$7x"

entering the command:

 
      call 'calltest.gp' "abcd" 1.2 + "'quoted'" -- "$2"

will display:

 
      argc=7 p0=abcd p1=1.2 p2=+ p3='quoted' p4=- p5=- p6=$2 p7=xx

NOTE: there is a clash in syntax with the datafile using callback operator. Use `$$n` or `column(n)` to access column n from a datafile inside a called datafile plot.


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2.3 clear

The clear command erases the current screen or output device as specified by output. This usually generates a formfeed on hardcopy devices. Use `set terminal` to set the device type.

For some terminals clear erases only the portion of the plotting surface defined by size, so for these it can be used in conjunction with multiplot to create an inset.

Example:

 
      set multiplot
      plot sin(x)
      set origin 0.5,0.5
      set size 0.4,0.4
      clear
      plot cos(x)
      unset multiplot

Please see multiplot, size, and origin for details of these commands.


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2.4 exit

The commands exit and quit, as well as the END-OF-FILE character (usually Ctrl-D) terminate input from the current input stream: terminal session, pipe, and file input (pipe).

If input streams are nested (inherited `load` scripts), then reading will continue in the parent stream. When the top level stream is closed, the program itself will exit.

The command `exit gnuplot` will immediately and unconditionally cause gnuplot to exit even if the input stream is multiply nested. In this case any open output files may not be completed cleanly. Example of use:

 
      bind "ctrl-x" "unset output; exit gnuplot"

See help for `batch/interactive` for more details.


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2.5 fit

The `fit` command can fit a user-defined function to a set of data points (x,y) or (x,y,z), using an implementation of the nonlinear least-squares (NLLS) Marquardt-Levenberg algorithm. Any user-defined variable occurring in the function body may serve as a fit parameter, but the return type of the function must be real.

Syntax:

 
      fit {[xrange] {[yrange]}} <function> '<datafile>'
          {datafile-modifiers}
          via '<parameter file>' | <var1>{,<var2>,...}

Ranges may be specified to temporarily limit the data which is to be fitted; any out-of-range data points are ignored. The syntax is

 
      [{dummy_variable=}{<min>}{:<max>}],

analogous to `plot`; see ranges.

<function> is any valid `gnuplot` expression, although it is usual to use a previously user-defined function of the form f(x) or f(x,y).

<datafile> is treated as in the `plot` command. All the datafile modifiers (using, every,...) except smooth and the deprecated thru are applicable to `fit`. See datafile.

The default data formats for fitting functions with a single independent variable, y=f(x), are {x:}y or x:y:s; those formats can be changed with the datafile using qualifier. The third item (a column number or an expression), if present, is interpreted as the standard deviation of the corresponding y value and is used to compute a weight for the datum, 1/s**2. Otherwise, all data points are weighted equally, with a weight of one. Note that if you don't specify a using option at all, no y deviations are read from the datafile even if it does have a third column, so you'll always get unit weights.

To fit a function with two independent variables, z=f(x,y), the required format is using with four items, x:y:z:s. The complete format must be given--no default columns are assumed for a missing token. Weights for each data point are evaluated from 's' as above. If error estimates are not available, a constant value can be specified as a constant expression (see using), e.g., `using 1:2:3:(1)`.

Multiple datasets may be simultaneously fit with functions of one independent variable by making y a 'pseudo-variable', e.g., the dataline number, and fitting as two independent variables. See multi-branch.

The `via` qualifier specifies which parameters are to be adjusted, either directly, or by referencing a parameter file.

Examples:

 
      f(x) = a*x**2 + b*x + c
      g(x,y) = a*x**2 + b*y**2 + c*x*y
      FIT_LIMIT = 1e-6
      fit f(x) 'measured.dat' via 'start.par'
      fit f(x) 'measured.dat' using 3:($7-5) via 'start.par'
      fit f(x) './data/trash.dat' using 1:2:3 via a, b, c
      fit g(x,y) 'surface.dat' using 1:2:3:(1) via a, b, c

After each iteration step, detailed information about the current state of the fit is written to the display. The same information about the initial and final states is written to a log file, "fit.log". This file is always appended to, so as to not lose any previous fit history; it should be deleted or renamed as desired. By using the command `set fit logfile`, the name of the log file can be changed.

If gnuplot was built with this option, and you activated it using `set fit errorvariables`, the error for each fitted parameter will be stored in a variable named like the parameter, but with "_err" appended. Thus the errors can be used as input for further computations.

The fit may be interrupted by pressing Ctrl-C (any key but Ctrl-C under MSDOS and Atari Multitasking Systems). After the current iteration completes, you have the option to (1) stop the fit and accept the current parameter values, (2) continue the fit, (3) execute a `gnuplot` command as specified by the environment variable FIT_SCRIPT. The default for FIT_SCRIPT is replot, so if you had previously plotted both the data and the fitting function in one graph, you can display the current state of the fit.

Once `fit` has finished, the update command may be used to store final values in a file for subsequent use as a parameter file. See update for details.


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2.5.1 adjustable parameters

There are two ways that `via` can specify the parameters to be adjusted, either directly on the command line or indirectly, by referencing a parameter file. The two use different means to set initial values.

Adjustable parameters can be specified by a comma-separated list of variable names after the `via` keyword. Any variable that is not already defined is created with an initial value of 1.0. However, the fit is more likely to converge rapidly if the variables have been previously declared with more appropriate starting values.

In a parameter file, each parameter to be varied and a corresponding initial value are specified, one per line, in the form

 
      varname = value

Comments, marked by '#', and blank lines are permissible. The special form

 
      varname = value       # FIXED

means that the variable is treated as a 'fixed parameter', initialized by the parameter file, but not adjusted by `fit`. For clarity, it may be useful to designate variables as fixed parameters so that their values are reported by `fit`. The keyword `# FIXED` has to appear in exactly this form.


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2.5.2 short introduction

`fit` is used to find a set of parameters that 'best' fits your data to your user-defined function. The fit is judged on the basis of the sum of the squared differences or 'residuals' (SSR) between the input data points and the function values, evaluated at the same places. This quantity is often called 'chisquare' (i.e., the Greek letter chi, to the power of 2). The algorithm attempts to minimize SSR, or more precisely, WSSR, as the residuals are 'weighted' by the input data errors (or 1.0) before being squared; see `fit error_estimates` for details.

That's why it is called 'least-squares fitting'. Let's look at an example to see what is meant by 'non-linear', but first we had better go over some terms. Here it is convenient to use z as the dependent variable for user-defined functions of either one independent variable, z=f(x), or two independent variables, z=f(x,y). A parameter is a user-defined variable that `fit` will adjust, i.e., an unknown quantity in the function declaration. Linearity/non-linearity refers to the relationship of the dependent variable, z, to the parameters which `fit` is adjusting, not of z to the independent variables, x and/or y. (To be technical, the second {and higher} derivatives of the fitting function with respect to the parameters are zero for a linear least-squares problem).

For linear least-squares (LLS), the user-defined function will be a sum of simple functions, not involving any parameters, each multiplied by one parameter. NLLS handles more complicated functions in which parameters can be used in a large number of ways. An example that illustrates the difference between linear and nonlinear least-squares is the Fourier series. One member may be written as

 
     z=a*sin(c*x) + b*cos(c*x).

If a and b are the unknown parameters and c is constant, then estimating values of the parameters is a linear least-squares problem. However, if c is an unknown parameter, the problem is nonlinear.

In the linear case, parameter values can be determined by comparatively simple linear algebra, in one direct step. However LLS is a special case which is also solved along with more general NLLS problems by the iterative procedure that `gnuplot` uses. `fit` attempts to find the minimum by doing a search. Each step (iteration) calculates WSSR with a new set of parameter values. The Marquardt-Levenberg algorithm selects the parameter values for the next iteration. The process continues until a preset criterion is met, either (1) the fit has "converged" (the relative change in WSSR is less than FIT_LIMIT), or (2) it reaches a preset iteration count limit, FIT_MAXITER (see variables). The fit may also be interrupted and subsequently halted from the keyboard (see `fit`). The user variable FIT_CONVERGED contains 1 if the previous fit command terminated due to convergence; it contains 0 if the previous fit terminated for any other reason.

Often the function to be fitted will be based on a model (or theory) that attempts to describe or predict the behaviour of the data. Then `fit` can be used to find values for the free parameters of the model, to determine how well the data fits the model, and to estimate an error range for each parameter. See `fit error_estimates`.

Alternatively, in curve-fitting, functions are selected independent of a model (on the basis of experience as to which are likely to describe the trend of the data with the desired resolution and a minimum number of parameters*functions.) The `fit` solution then provides an analytic representation of the curve.

However, if all you really want is a smooth curve through your data points, the smooth option to `plot` may be what you've been looking for rather than `fit`.


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2.5.3 error estimates

In `fit`, the term "error" is used in two different contexts, data error estimates and parameter error estimates.

Data error estimates are used to calculate the relative weight of each data point when determining the weighted sum of squared residuals, WSSR or chisquare. They can affect the parameter estimates, since they determine how much influence the deviation of each data point from the fitted function has on the final values. Some of the `fit` output information, including the parameter error estimates, is more meaningful if accurate data error estimates have been provided.

The 'statistical overview' describes some of the `fit` output and gives some background for the 'practical guidelines'.


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2.5.3.1 statistical overview

The theory of non-linear least-squares (NLLS) is generally described in terms of a normal distribution of errors, that is, the input data is assumed to be a sample from a population having a given mean and a Gaussian (normal) distribution about the mean with a given standard deviation. For a sample of sufficiently large size, and knowing the population standard deviation, one can use the statistics of the chisquare distribution to describe a "goodness of fit" by looking at the variable often called "chisquare". Here, it is sufficient to say that a reduced chisquare (chisquare/degrees of freedom, where degrees of freedom is the number of datapoints less the number of parameters being fitted) of 1.0 is an indication that the weighted sum of squared deviations between the fitted function and the data points is the same as that expected for a random sample from a population characterized by the function with the current value of the parameters and the given standard deviations.

If the standard deviation for the population is not constant, as in counting statistics where variance = counts, then each point should be individually weighted when comparing the observed sum of deviations and the expected sum of deviations.

At the conclusion `fit` reports 'stdfit', the standard deviation of the fit, which is the rms of the residuals, and the variance of the residuals, also called 'reduced chisquare' when the data points are weighted. The number of degrees of freedom (the number of data points minus the number of fitted parameters) is used in these estimates because the parameters used in calculating the residuals of the datapoints were obtained from the same data. These values are exported to the variables

 
      FIT_NDF = Number of degrees of freedom
      FIT_WSSR = Weighted sum-of-squares residual
      FIT_STDFIT = sqrt(WSSR/NDF)

To estimate confidence levels for the parameters, one can use the minimum chisquare obtained from the fit and chisquare statistics to determine the value of chisquare corresponding to the desired confidence level, but considerably more calculation is required to determine the combinations of parameters which produce such values.

Rather than determine confidence intervals, `fit` reports parameter error estimates which are readily obtained from the variance-covariance matrix after the final iteration. By convention, these estimates are called "standard errors" or "asymptotic standard errors", since they are calculated in the same way as the standard errors (standard deviation of each parameter) of a linear least-squares problem, even though the statistical conditions for designating the quantity calculated to be a standard deviation are not generally valid for the NLLS problem. The asymptotic standard errors are generally over-optimistic and should not be used for determining confidence levels, but are useful for qualitative purposes.

The final solution also produces a correlation matrix, which gives an indication of the correlation of parameters in the region of the solution; if one parameter is changed, increasing chisquare, does changing another compensate? The main diagonal elements, autocorrelation, are all 1; if all parameters were independent, all other elements would be nearly 0. Two variables which completely compensate each other would have an off-diagonal element of unit magnitude, with a sign depending on whether the relation is proportional or inversely proportional. The smaller the magnitudes of the off-diagonal elements, the closer the estimates of the standard deviation of each parameter would be to the asymptotic standard error.


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2.5.3.2 practical guidelines

If you have a basis for assigning weights to each data point, doing so lets you make use of additional knowledge about your measurements, e.g., take into account that some points may be more reliable than others. That may affect the final values of the parameters.

Weighting the data provides a basis for interpreting the additional `fit` output after the last iteration. Even if you weight each point equally, estimating an average standard deviation rather than using a weight of 1 makes WSSR a dimensionless variable, as chisquare is by definition.

Each fit iteration will display information which can be used to evaluate the progress of the fit. (An '*' indicates that it did not find a smaller WSSR and is trying again.) The 'sum of squares of residuals', also called 'chisquare', is the WSSR between the data and your fitted function; `fit` has minimized that. At this stage, with weighted data, chisquare is expected to approach the number of degrees of freedom (data points minus parameters). The WSSR can be used to calculate the reduced chisquare (WSSR/ndf) or stdfit, the standard deviation of the fit, sqrt(WSSR/ndf). Both of these are reported for the final WSSR.

If the data are unweighted, stdfit is the rms value of the deviation of the data from the fitted function, in user units.

If you supplied valid data errors, the number of data points is large enough, and the model is correct, the reduced chisquare should be about unity. (For details, look up the 'chi-squared distribution' in your favourite statistics reference.) If so, there are additional tests, beyond the scope of this overview, for determining how well the model fits the data.

A reduced chisquare much larger than 1.0 may be due to incorrect data error estimates, data errors not normally distributed, systematic measurement errors, 'outliers', or an incorrect model function. A plot of the residuals, e.g., `plot 'datafile' using 1:($2-f($1))`, may help to show any systematic trends. Plotting both the data points and the function may help to suggest another model.

Similarly, a reduced chisquare less than 1.0 indicates WSSR is less than that expected for a random sample from the function with normally distributed errors. The data error estimates may be too large, the statistical assumptions may not be justified, or the model function may be too general, fitting fluctuations in a particular sample in addition to the underlying trends. In the latter case, a simpler function may be more appropriate.

You'll have to get used to both `fit` and the kind of problems you apply it to before you can relate the standard errors to some more practical estimates of parameter uncertainties or evaluate the significance of the correlation matrix.

Note that `fit`, in common with most NLLS implementations, minimizes the weighted sum of squared distances (y-f(x))**2. It does not provide any means to account for "errors" in the values of x, only in y. Also, any "outliers" (data points outside the normal distribution of the model) will have an exaggerated effect on the solution.


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2.5.4 control

There are a number of `gnuplot` variables that can be defined to affect `fit`. Those which can be defined once `gnuplot` is running are listed under 'control_variables' while those defined before starting `gnuplot` are listed under 'environment_variables'.


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2.5.4.1 control variables

The default epsilon limit (1e-5) may be changed by declaring a value for

 
      FIT_LIMIT

When the sum of squared residuals changes between two iteration steps by a factor less than this number (epsilon), the fit is considered to have 'converged'.

The maximum number of iterations may be limited by declaring a value for

 
      FIT_MAXITER

A value of 0 (or not defining it at all) means that there is no limit.

If you need even more control about the algorithm, and know the Marquardt-Levenberg algorithm well, there are some more variables to influence it. The startup value of `lambda` is normally calculated automatically from the ML-matrix, but if you want to, you may provide your own one with

 
      FIT_START_LAMBDA

Specifying FIT_START_LAMBDA as zero or less will re-enable the automatic selection. The variable

 
      FIT_LAMBDA_FACTOR

gives the factor by which `lambda` is increased or decreased whenever the chi-squared target function increased or decreased significantly. Setting FIT_LAMBDA_FACTOR to zero re-enables the default factor of 10.0.

Other variables with the FIT_ prefix may be added to `fit`, so it is safer not to use that prefix for user-defined variables.

The variables FIT_SKIP and FIT_INDEX were used by earlier releases of `gnuplot` with a 'fit' patch called `gnufit` and are no longer available. The datafile every modifier provides the functionality of FIT_SKIP. FIT_INDEX was used for multi-branch fitting, but multi-branch fitting of one independent variable is now done as a pseudo-3D fit in which the second independent variable and using are used to specify the branch. See multi-branch.


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2.5.4.2 environment variables

The environment variables must be defined before `gnuplot` is executed; how to do so depends on your operating system.

 
      FIT_LOG

changes the name (and/or path) of the file to which the fit log will be written from the default of "fit.log" in the working directory. The default value can be overwritten using the command `set fit logfile`.

 
      FIT_SCRIPT

specifies a command that may be executed after an user interrupt. The default is replot, but a `plot` or `load` command may be useful to display a plot customized to highlight the progress of the fit.


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2.5.5 multi-branch

In multi-branch fitting, multiple data sets can be simultaneously fit with functions of one independent variable having common parameters by minimizing the total WSSR. The function and parameters (branch) for each data set are selected by using a 'pseudo-variable', e.g., either the dataline number (a 'column' index of -1) or the datafile index (-2), as the second independent variable.

Example: Given two exponential decays of the form, z=f(x), each describing a different data set but having a common decay time, estimate the values of the parameters. If the datafile has the format x:z:s, then

 
     f(x,y) = (y==0) ? a*exp(-x/tau) : b*exp(-x/tau)
     fit f(x,y) 'datafile' using  1:-2:2:3  via a, b, tau

For a more complicated example, see the file "hexa.fnc" used by the "fit.dem" demo.

Appropriate weighting may be required since unit weights may cause one branch to predominate if there is a difference in the scale of the dependent variable. Fitting each branch separately, using the multi-branch solution as initial values, may give an indication as to the relative effect of each branch on the joint solution.


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2.5.6 starting values

Nonlinear fitting is not guaranteed to converge to the global optimum (the solution with the smallest sum of squared residuals, SSR), and can get stuck at a local minimum. The routine has no way to determine that; it is up to you to judge whether this has happened.

`fit` may, and often will get "lost" if started far from a solution, where SSR is large and changing slowly as the parameters are varied, or it may reach a numerically unstable region (e.g., too large a number causing a floating point overflow) which results in an "undefined value" message or `gnuplot` halting.

To improve the chances of finding the global optimum, you should set the starting values at least roughly in the vicinity of the solution, e.g., within an order of magnitude, if possible. The closer your starting values are to the solution, the less chance of stopping at another minimum. One way to find starting values is to plot data and the fitting function on the same graph and change parameter values and replot until reasonable similarity is reached. The same plot is also useful to check whether the fit stopped at a minimum with a poor fit.

Of course, a reasonably good fit is not proof there is not a "better" fit (in either a statistical sense, characterized by an improved goodness-of-fit criterion, or a physical sense, with a solution more consistent with the model.) Depending on the problem, it may be desirable to `fit` with various sets of starting values, covering a reasonable range for each parameter.


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2.5.7 tips

Here are some tips to keep in mind to get the most out of `fit`. They're not very organized, so you'll have to read them several times until their essence has sunk in.

The two forms of the `via` argument to `fit` serve two largely distinct purposes. The `via "file"` form is best used for (possibly unattended) batch operation, where you just supply the startup values in a file and can later use update to copy the results back into another (or the same) parameter file.

The `via var1, var2, ...` form is best used interactively, where the command history mechanism may be used to edit the list of parameters to be fitted or to supply new startup values for the next try. This is particularly useful for hard problems, where a direct fit to all parameters at once won't work without good starting values. To find such, you can iterate several times, fitting only some of the parameters, until the values are close enough to the goal that the final fit to all parameters at once will work.

Make sure that there is no mutual dependency among parameters of the function you are fitting. For example, don't try to fit a*exp(x+b), because a*exp(x+b)=a*exp(b)*exp(x). Instead, fit either a*exp(x) or exp(x+b).

A technical issue: the parameters must not be too different in magnitude. The larger the ratio of the largest and the smallest absolute parameter values, the slower the fit will converge. If the ratio is close to or above the inverse of the machine floating point precision, it may take next to forever to converge, or refuse to converge at all. You will have to adapt your function to avoid this, e.g., replace 'parameter' by '1e9*parameter' in the function definition, and divide the starting value by 1e9.

If you can write your function as a linear combination of simple functions weighted by the parameters to be fitted, by all means do so. That helps a lot, because the problem is no longer nonlinear and should converge with only a small number of iterations, perhaps just one.

Some prescriptions for analysing data, given in practical experimentation courses, may have you first fit some functions to your data, perhaps in a multi-step process of accounting for several aspects of the underlying theory one by one, and then extract the information you really wanted from the fitting parameters of those functions. With `fit`, this may often be done in one step by writing the model function directly in terms of the desired parameters. Transforming data can also quite often be avoided, though sometimes at the cost of a more difficult fit problem. If you think this contradicts the previous paragraph about simplifying the fit function, you are correct.

A "singular matrix" message indicates that this implementation of the Marquardt-Levenberg algorithm can't calculate parameter values for the next iteration. Try different starting values, writing the function in another form, or a simpler function.

Finally, a nice quote from the manual of another fitting package (fudgit), that kind of summarizes all these issues: "Nonlinear fitting is an art!"


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2.6 help

The help command displays on-line help. To specify information on a particular topic use the syntax:

 
      help {<topic>}

If <topic> is not specified, a short message is printed about `gnuplot`. After help for the requested topic is given, a menu of subtopics is given; help for a subtopic may be requested by typing its name, extending the help request. After that subtopic has been printed, the request may be extended again or you may go back one level to the previous topic. Eventually, the `gnuplot` command line will return.

If a question mark (?) is given as the topic, the list of topics currently available is printed on the screen.


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2.7 history

`history` command lists or saves previous entries in the history of the command line editing, or executes an entry.

Here you find 'usage by examples':

 
      history               # show the complete history
      history 5             # show last 5 entries in the history
      history quiet 5       # show last 5 entries without entry numbers
      history "hist.gp"     # write the complete history to file hist.gp
      history "hist.gp" append # append the complete history to file hist.gp
      history 10 "hist.gp"  # write last 10 commands to file hist.gp
      history 10 "|head -5 >>diary.gp" # write 5 history commands using pipe
      history ?load         # show all history entries starting with "load"
      history ?"set c"      # like above, several words enclosed in quotes
      hi !reread            # execute last entry starting with "reread"
      hist !"set xr"        # like above, several words enclosed in quotes
      hi !hi                # guess yourself :-))

On systems which support a popen function (Unix), the output of history can be piped through an external program by starting the file name with a '|', as one of the above examples demonstrates.


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2.8 if

The if command allows commands to be executed conditionally.

Syntax:

 
      if (<condition>) <command-line> [; else if (<condition>) ...; else ...]

<condition> will be evaluated. If it is true (non-zero), then the command(s) of the <command-line> will be executed. If <condition> is false (zero), then the entire <command-line> is ignored until the next occurrence of `else`. Note that use of `;` to allow multiple commands on the same line will _not_ end the conditionalized commands.

Examples:

 
      pi=3
      if (pi!=acos(-1)) print "?Fixing pi!"; pi=acos(-1); print pi

will display:

 
      ?Fixing pi!
      3.14159265358979

but

 
      if (1==2) print "Never see this"; print "Or this either"

will not display anything.

else:

 
      v=0
      v=v+1; if (v%2) print "2" ; else if (v%3) print "3"; else print "fred"

(repeat the last line repeatedly!)

See reread for an example of how if and reread can be used together to perform a loop.


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2.9 load

The `load` command executes each line of the specified input file as if it had been typed in interactively. Files created by the save command can later be `load`ed. Any text file containing valid commands can be created and then executed by the `load` command. Files being `load`ed may themselves contain `load` or call commands. See `comments` for information about comments in commands. To `load` with arguments, see call.

The `load` command _must_ be the last command on a multi-command line.

Syntax:

 
      load "<input-file>"

The name of the input file must be enclosed in quotes.

The special filename "-" may be used to `load` commands from standard input. This allows a `gnuplot` command file to accept some commands from standard input. Please see help for `batch/interactive` for more details.

On some systems which support a popen function (Unix), the load file can be read from a pipe by starting the file name with a '<'.

Examples:

 
      load 'work.gnu'
      load "func.dat"
      load "< loadfile_generator.sh"

The `load` command is performed implicitly on any file names given as arguments to `gnuplot`. These are loaded in the order specified, and then `gnuplot` exits.


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2.10 lower

Syntax:

 
      lower {plot_window_nb}

The lower command lowers (opposite to raise) plot window(s) associated with the interactive terminal of your gnuplot session, i.e. `pm`, `win`, `wxt` or `x11`. It puts the plot window to bottom in the z-order windows stack of the window manager of your desktop.

As `x11` and `wxt` support multiple plot windows, then by default they lower these windows in descending order of most recently created on top to the least recently created on bottom. If a plot number is supplied as an optional parameter, only the associated plot window will be lowered if it exists.

The optional parameter is ignored for single plot-window terminals, i.e. `pm` and `win`.


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2.11 pause

The pause command displays any text associated with the command and then waits a specified amount of time or until the carriage return is pressed. pause is especially useful in conjunction with `load` files.

Syntax:

 
      pause <time> {"<string>"}
      pause mouse {<endcondition>}{, <endcondition>} {"<string>"}

<time> may be any constant or expression. Choosing -1 will wait until a carriage return is hit, zero (0) won't pause at all, and a positive number will wait the specified number of seconds. The time is rounded to an integer number of seconds if subsecond time resolution is not supported by the given platform. `pause 0` is synonymous with `print`.

If the current terminal supports mousing, then `pause mouse` will terminate on either a mouse click or on ctrl-C. For all other terminals, or if mousing is not active, `pause mouse` is equivalent to `pause -1`.

If one or more end conditions are given after `pause mouse`, then any one of the conditions will terminate the pause. The possible end conditions are `keypress`, `button1`, `button2`, `button3`, and `any`. If the pause terminates on a keypress, then the ascii value of the key pressed is returned in MOUSE_KEY. The character itself is returned as a one character string in MOUSE_CHAR.

In all cases the coordinates of the mouse are returned in variables MOUSE_X, MOUSE_Y, MOUSE_X2, MOUSE_Y2. See variables.

Note: Since pause communicates with the operating system rather than the graphics, it may behave differently with different device drivers (depending upon how text and graphics are mixed).

Examples:

 
      pause -1    # Wait until a carriage return is hit
      pause 3     # Wait three seconds
      pause -1  "Hit return to continue"
      pause 10  "Isn't this pretty?  It's a cubic spline."
      pause mouse "Click any mouse button on selected data point"
      pause mouse keypress "Type a letter from A-F in the active window"
      pause mouse button1,keypress
      pause mouse any "Any key or button will terminate"

The variant "pause mouse key" will resume after any keypress in the active plot window. If you want to wait for a particular key to be pressed, you can use a reread loop such as:

 
      printf "I will resume after you hit the Tab key in the plot window"
      load "wait_for_tab"

File "wait_for_tab" contains the lines

 
      pause mouse key
      if (MOUSE_KEY != 9) reread


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2.12 plot

`plot` is the primary command for drawing plots with `gnuplot`. It creates plots of functions and data in many, many ways. `plot` is used to draw 2-d functions and data; `splot` draws 2-d projections of 3-d surfaces and data. `plot` and `splot` contain many common features; see `splot` for differences. Note specifically that although the `binary <binary list>` variation does work for both `plot` and `splot`, there are small differences between these modes. Furthermore, `plot`'s `axes` option does not exist for `splot`.

Syntax:

 
      plot {<ranges>}
           {<function> | {"<datafile>" {datafile-modifiers}}}
           {axes <axes>} {<title-spec>} {with <style>}
           {, {definitions,} <function> ...}

where either a <function> or the name of a data file enclosed in quotes is supplied. A function is a mathematical expression or a pair of mathematical expressions in parametric mode. The expressions may be defined completely or in part earlier in the stream of `gnuplot` commands (see `user-defined`).

It is also possible to define functions and parameters on the `plot` command itself. This is done merely by isolating them from other items with commas.

There are four possible sets of axes available; the keyword <axes> is used to select the axes for which a particular line should be scaled. `x1y1` refers to the axes on the bottom and left; `x2y2` to those on the top and right; `x1y2` to those on the bottom and right; and `x2y1` to those on the top and left. Ranges specified on the `plot` command apply only to the first set of axes (bottom left).

Examples:

 
      plot sin(x)
      plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x)
      plot [t=1:10] [-pi:pi*2] tan(t), \
           "data.1" using (tan($2)):($3/$4) smooth csplines \
                    axes x1y2 notitle with lines 5

See also `show plot`.


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2.12.1 data

Discrete data contained in a file can be displayed by specifying the name of the data file (enclosed in single or double quotes) on the `plot` command line.

Syntax:

 
      plot '<file_name>' {binary <binary list>}
                         {matrix}
                         {index <index list>}
                         {every <every list>}
                         {thru <thru expression>}
                         {using <using list>}
                         {smooth <option>}

The modifiers `binary`, index, every, thru, using, and smooth are discussed separately. In brief, `binary` allows data entry from a binary file (default is ASCII), index selects which data sets in a multi-data-set file are to be plotted, every specifies which points within a single data set are to be plotted, using determines how the columns within a single record are to be interpreted (thru is a special case of using), and smooth allows for simple interpolation and approximation. (`splot` has a similar syntax, but does not support the smooth and thru options.)

ASCII DATA FILES:

Data files should contain at least one data point per record (using can select one data point from the record). Records beginning with `#` (and also with `!` on VMS) will be treated as comments and ignored. Each data point represents an (x,y) pair. For `plot`s with error bars or error bars with lines (see errorbars or errorlines), each data point is (x,y,ydelta), (x,y,ylow,yhigh), (x,y,xdelta), (x,y,xlow,xhigh), or (x,y,xlow,xhigh,ylow,yhigh).

In all cases, the numbers of each record of a data file must be separated by white space (one or more blanks or tabs) unless a format specifier is provided by the using option. This white space divides each record into columns. However, whitespace inside a pair of double quotes is ignored when counting columns, so the following datafile line has three columns:

 
      1.0 "second column" 3.0

Data may be written in exponential format with the exponent preceded by the letter e or E. The fortran exponential specificiers d, D, q, and Q may also be used if the command `set datafile fortran` is in effect.

Only one column (the y value) need be provided. If x is omitted, `gnuplot` provides integer values starting at 0.

In datafiles, blank records (records with no characters other than blanks and a newline and/or carriage return) are significant--pairs of blank records separate indexes (see index). Data separated by double blank records are treated as if they were in separate data files.

Single blank records designate discontinuities in a `plot`; no line will join points separated by a blank records (if they are plotted with a line style).

If autoscaling has been enabled (autoscale), the axes are automatically extended to include all datapoints, with a whole number of tic marks if tics are being drawn. This has two consequences: i) For `splot`, the corner of the surface may not coincide with the corner of the base. In this case, no vertical line is drawn. ii) When plotting data with the same x range on a dual-axis graph, the x coordinates may not coincide if the x2tics are not being drawn. This is because the x axis has been autoextended to a whole number of tics, but the x2 axis has not. The following example illustrates the problem:

 
      reset; plot '-', '-' axes x2y1
      1 1
      19 19
      e
      1 1
      19 19
      e

To avoid this, you can use the `fixmin`/`fixmax` feature of the autoscale command, which turns off the automatic extension of the axis range upto the next tic mark.

BINARY DATA FILES:

Gnuplot can read binary data files. However, adequate information about details of the file format must be given on the command line or extracted from the file itself for a supported binary `filetype`. In particular, there are two structures for binary files, a matrix binary format and a general binary format.

The matrix binary format contains a two dimensional array of 32 bit IEEE float values with an additional column and row of coordinate values. As with ASCII matrix, in the using list, repetition of the coordinate row constitutes column 1, repetition of the coordinate column constitutes column 2, and the array of values constitutes column 3.

The general binary format contains an arbitrary number of columns for which information must be specified at the command line. For example, `array`, `record`, `format` and using can indicate the size, format and dimension of data. There are a variety of useful commands for skipping file headers and changing endianess. There are a set of commands for positioning and translating data since often coordinates are not part of the file when uniform sampling is inherent in the data. Different from matrix binary or ASCII, general binary does not treat the generated columns as 1, 2 or 3 in the using list. Rather, column 1 begins with column 1 of the file, or as specified in the `format` list.

There are global default settings for the various binary options which may be set using the same syntax as the options when used as part of the `(s)plot <filename> binary ...` command. This syntax is `set datafile binary ...`. The general rule is that common command-line specified parameters override file-extracted parameters which override default parameters.

Matrix binary is the default binary format when no keywords specific to general binary are given, i.e., `array`, `record`, `format`, `filetype`.

General binary data can be entered at the command line via the special file name '-'. However, this is intended for use through a pipe where programs can exchange binary data, not for keyboards. There is no "end of record" character for binary data. Gnuplot continues reading from a pipe until it has read the number of points declared in the `array` qualifier.

See `datafile binary` for more details.


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2.12.1.1 binary

The `binary` keyword allows a data file to be binary as opposed to ASCII. There are two formats for binary-matrix binary and general binary. Matrix binary is a fixed format in which data appears in a 2D array with an extra row and column for coordinate values. General binary is a flexible format for which details about the file must be given at the command line.

See `binary matrix` or `binary general` for more details.


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2.12.1.2 binary general

General binary data in which format information is not necessarily part of the file can be read by giving further details about the file format at the command line. Although the syntax is slightly arcane to the casual user, general binary is particularly useful for application programs using gnuplot and sending large amounts of data.

Syntax:

 
      plot '<file_name>' {binary <binary list>} ...
      splot '<file_name>' {binary <binary list>} ...

General binary format is activated by keywords in <binary list> pertaining to information about file structure, i.e., `array`, `record`, `format` or `filetype`. Otherwise, matrix binary format is assumed. (See `binary matrix` for more details.)

There are some standard file types that may be read for which details about the binary format may be extracted automatically. (Type `show datafile binary` at the command line for a list.) Otherwise, details must be specified at the command line or set in the defaults. Keywords are described below.

The keyword `filetype` in <binary list> controls the routine used to read the file, i.e., the format of the data. For a list of the supported file types, type `show datafile binary filetypes`. If no file type is given, the rule is that traditional gnuplot binary is assumed for `splot` if the `binary` keyword stands alone. In all other circumstances, for `plot` or when one of the <binary list> keywords appears, a raw binary file is assumed whereby the keywords specify the binary format.

General binary data files fall into two basic classes, and some files may be of both classes depending upon how they are treated. There is that class for which uniform sampling is assumed and point coordinates must be generated. This is the class for which full control via the <binary list> keywords applies. For this class, the settings precedence is that command line parameters override in-file parameters, which override default settings. The other class is that set of files for which coordinate information is contained within the file or there is possibly a non-uniform sampling such as gnuplot binary.

Other than for the unique data files such as gnuplot binary, one should think of binary data as conceptually the same as ASCII data. Each point has columns of information which are selected via the `<using list>` associated with using. When no `format` string is specified, gnuplot will retrieve a number of binary variables equal to the largest column given in the `<using list>`. For example, `using 1:3` will result in three columns being read, of which the second will be ignored. There are default using lists based upon the typical number of parameters associated with a certain plot type. For example, `with image` has a default of `using 1`, while `with rgbimage` has a default of `using 1:2:3`. Note that the special characters for using representing point/line/index generally should not be used for binary data. There are keywords in <binary list> that control this.

-- ARRAY --

Describes the sampling array dimensions associated with the binary file. The coordinates will be generated by gnuplot. A number must be specified for each dimension, thereby calling out the size of the array. For example, `array=10x20` means the underlying sampling structure is two-dimensional with 10 points along the first (x) dimension and 20 points along the second (y) dimension. A special "number", `Inf`, can be used to indicate that data should be read until the end of file. A colon can be used to separate the dimensions for multiple records. For example, `array=25:35` indicates there are two one-dimensional records within the file. The colon behavior applies to the remaining keywords in this list for which it makes sense to be associated with individual records.

Currently, syntax allows for up to three-dimensional arrays. However, no conventions have yet been made for handling three-dimensional coordinates.

-- RECORD --

This keyword serves the same function as `array`, having the same syntax. However, `record` causes gnuplot to not generate coordinate information. This is for the case where such information may be included in one of the columns of the binary data file.

-- FORMAT --

The default binary format is a float. For more flexibility, the format can include details about variable sizes. For example, `format="%uchar%int%float"` associates an unsigned character with the first using column, an int with the second column and a float with the third column. If the number of size specifications is less than the greatest column number, the size is implicitly taken to be similar to the last given variable size.

Furthermore, the format specification can include "discarded" terms via the `*` character. For example, to skip the middle column of the previous example, one could write `format="%uchar%*int%float"` and gnuplot will discard the middle integer. To list variable sizes, type `show datafile binary datasizes`. There are a group of names that are machine dependent along with their sizes in bytes for the particular compilation. There is also a group of names which attempt to be machine independent.

-- ENDIAN --

Often the endianess of binary data in the file does not agree with the endianess used by the platform on which gnuplot is running. Several words can direct gnuplot how to arrange bytes. For example `endian=little` means treat the binary file as having byte significance from least to greatest. The options are

 
              little:  least significant to greatest significance
                 big:  greatest significance to least significance
             default:  assume file endianess is the same as compiler
         swap (swab):  Interchange the significance.  (If things
                       don't look right, try this.)

Gnuplot can support "middle" ("pdp") endian if it is compiled with that option.

-- FILETYPE --

For some standard binary file formats gnuplot can extract all the necessary information from the file in question. As an example, "format=edf" will read ESRF Header File format files. For a list of the currently supported file formats, type `show datafile binary filetypes`.

There is a special file type called `auto` for which gnuplot will check if the binary file's extension is a quasi-standard extension for a supported format.

Command line keywords may be used to override settings extracted from the file. The settings from the file override any defaults. (See `set datafile binary` for details.)

-- AVS --

`avs` is one of the automatically recognized binary file types for images. AVS is an extremely simple format, suitable mostly for streaming between applications. It consists of 2 longs (xwidth, ywidth) followed by a stream of pixels, each with four bytes of information alpha/red/green/blue.

-- EDF --

`edf` is one of the automatically recognized binary file types for images. EDF stands for ESRF Data Format, and it supports both edf and ehf formats (the latter means ESRF Header Format). More information on specifications can be found at

 
  http://www.esrf.fr/computing/expg/subgroups/general/format/Format.html

See also `binary`.

-- KEYWORDS --

The following keywords apply only when generating coordinates. That is, when the keyword `array` is used.

-- SCAN --

A great deal of confusion can arise concerning the relationship between how gnuplot scans a binary file and the dimensions seen on the plot. To lessen the confusion, conceptually think of gnuplot _always_ scanning the binary file point/line/plane or fast/medium/slow. Then this keyword is used to tell gnuplot how to map this scanning convention to the Cartesian convention shown in plots, i.e., x/y/z. The qualifier for scan is a two or three letter code representing where point is assigned (first letter), line is assigned (second letter), and plane is assigned (third letter). For example, `scan=yx` means the fastest, point-by-point, increment should be mapped along the Cartesian y dimension and the middle, line-by-line, increment should be mapped along the x dimension.

When the plotting mode is `plot`, the qualifier code can include the two letters x and y. For `splot`, it can include the three letters x, y and z.

There is nothing restricting the inherent mapping from point/line/plane to apply only to Cartesian coordinates. For this reason there are cylindrical coordinate synonyms for the qualifier codes where t (theta), r and z are analogous to the x, y and z of Cartesian coordinates.

-- TRANSPOSE --

Shorthand notation for `scan=yx` or `scan=yxz`.

-- DX, DY, DZ --

When gnuplot generates coordinates, it uses the spacing described by these keywords. For example `dx=10 dy=20` would mean space samples along the x dimension by 10 and space samples along the y dimension by 20. `dy` cannot appear if `dx` does not appear. Similarly, `dz` cannot appear if `dy` does not appear. If the underlying dimensions are greater than the keywords specified, the spacing of the highest dimension given is extended to the other dimensions. For example, if an image is being read from a file and only `dx=3.5` is given gnuplot uses a delta x and delta y of 3.5.

The following keywords also apply only when generating coordinates. However they may also be used with matrix binary files.

-- FLIPX, FLIPY, FLIPZ --

Sometimes the scanning directions in a binary datafile are not consistent with that assumed by gnuplot. These keywords can flip the scanning direction along dimensions x, y, z.

-- ORIGIN --

When gnuplot generates coordinates based upon transposition and flip, it attempts to always position the lower left point in the array at the origin, i.e., the data lies in the first quadrant of a Cartesian system after transpose and flip.

To position the array somewhere else on the graph, the origin keyword directs gnuplot to position the lower left point of the array at a point specified by a tuple. The tuple should be a double for `plot` and a triple for `splot`. For example, `origin=(100,100):(100,200)` is for two records in the file and intended for plotting in two dimensions. A second example, `origin=(0,0,3.5)`, is for plotting in three dimensions.

-- CENTER --

Similar to origin, this keyword will position the array such that its center lies at the point given by the tuple. For example, `center=(0,0)`. Center does not apply when the size of the array is `Inf`.

-- ROTATE --

The transpose and flip commands provide some flexibility in generating and orienting coordinates. However, for full degrees of freedom, it is possible to apply a rotational vector described by a rotational angle in two dimensions.

The `rotate` keyword applies to the two-dimensional plane, whether it be `plot` or `splot`. The rotation is done with respect to the positive angle of the Cartesian plane.

The angle can be expressed in radians, radians as a multiple of pi, or degrees. For example, `rotate=1.5708`, `rotate=0.5pi` and `rotate=90deg` are equivalent.

If origin is specified, the rotation is done about the lower left sample point before translation. Otherwise, the rotation is done about the array `center`.

-- PERPENDICULAR --

For `splot`, the concept of a rotational vector is implemented by a triple representing the vector to be oriented normal to the two-dimensional x-y plane. Naturally, the default is (0,0,1). Thus specifying both rotate and perpendicular together can orient data myriad ways in three-space.

The two-dimensional rotation is done first, followed by the three-dimensional rotation. That is, if R' is the rotational 2 x 2 matrix described by an angle, and P is the 3 x 3 matrix projecting (0,0,1) to (xp,yp,zp), let R be constructed from R' at the upper left sub-matrix, 1 at element 3,3 and zeros elsewhere. Then the matrix formula for translating data is v' = P R v, where v is the 3 x 1 vector of data extracted from the data file. In cases where the data of the file is inherently not three-dimensional, logical rules are used to place the data in three-space. (E.g., usually setting the z-dimension value to zero and placing 2D data in the x-y plane.)

-- BINARY EXAMPLES --

Examples:

 
      # Selects two float values (second one implicit) with a float value
      # discarded between them for an indefinite length of 1D data.
      plot '<file_name>' binary format="%float%*float" using 1:2 with lines

 
      # The data file header contains all details necessary for creating
      # coordinates from an EDF file.
      plot '<file_name>' binary filetype=edf with image
      plot '<file_name>.edf' binary filetype=auto with image

 
      # Selects three unsigned characters for components of a raw RGB image
      # and flips the y-dimension so that typical image orientation (start
      # at top left corner) translates to the Cartesian plane.  Pixel
      # spacing is given and there are two images in the file.  One of them
      # is translated via origin.
      plot '<file_name>' binary array=512x1024:1024x512 format='%uchar' \
           dx=2:1 dy=1:2 origin=(0,0):(1024,1024) flipy u 1:2:3 w rgbimage

 
      # Four separate records in which the coordinates are part of the
      # data file.  The file was created with a endianess different from
      # the system on which gnuplot is running.
      splot '<file_name>' binary record=30:30:29:26 endian=swap u 1:2:3

See also `binary matrix`.


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2.12.1.3 every

The every keyword allows a periodic sampling of a data set to be plotted.

In the discussion a "point" is a datum defined by a single record in the file; "block" here will mean the same thing as "datablock" (see `glossary`).

Syntax:

 
      plot 'file' every {<point_incr>}
                          {:{<block_incr>}
                            {:{<start_point>}
                              {:{<start_block>}
                                {:{<end_point>}
                                  {:<end_block>}}}}}

The data points to be plotted are selected according to a loop from <`start_point`> to <`end_point`> with increment <`point_incr`> and the blocks according to a loop from <`start_block`> to <`end_block`> with increment <`block_incr`>.

The first datum in each block is numbered '0', as is the first block in the file.

Note that records containing unplottable information are counted.

Any of the numbers can be omitted; the increments default to unity, the start values to the first point or block, and the end values to the last point or block. If every is not specified, all points in all lines are plotted.

Examples:

 
      every :::3::3    # selects just the fourth block ('0' is first)
      every :::::9     # selects the first 10 blocks
      every 2:2        # selects every other point in every other block
      every ::5::15    # selects points 5 through 15 in each block

See simple plot demos (simple.dem) , Non-parametric splot demos , and Parametric splot demos .


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2.12.1.4 example datafile

This example plots the data in the file "population.dat" and a theoretical curve:

 
      pop(x) = 103*exp((1965-x)/10)
      plot [1960:1990] 'population.dat', pop(x)

The file "population.dat" might contain:

 
      # Gnu population in Antarctica since 1965
         1965   103
         1970   55
         1975   34
         1980   24
         1985   10


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2.12.1.5 index

The index keyword allows only some of the data sets in a multi-data-set file to be plotted.

Syntax:

 
      plot 'file' index <m>{{:<n>}:<p>}

Data sets are separated by pairs of blank records. `index <m>` selects only set <m>; `index <m>:<n>` selects sets in the range <m> to <n>; and `index <m>:<n>:<p>` selects indices <m>, <m>+<p>, <m>+2<p>, etc., but stopping at <n>. Following C indexing, the index 0 is assigned to the first data set in the file. Specifying too large an index results in an error message. If index is not specified, all sets are plotted as a single data set.

Example:

 
      plot 'file' index 4:5

splot with indices demo.


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2.12.1.6 smooth

`gnuplot` includes a few general-purpose routines for interpolation and approximation of data; these are grouped under the smooth option. More sophisticated data processing may be performed by preprocessing the data externally or by using `fit` with an appropriate model.

Syntax:

 
      smooth {unique | frequency | csplines | acsplines | bezier | sbezier}

`unique` and `frequency` plot the data after making them monotonic. Each of the other routines uses the data to determine the coefficients of a continuous curve between the endpoints of the data. This curve is then plotted in the same manner as a function, that is, by finding its value at uniform intervals along the abscissa (see samples) and connecting these points with straight line segments (if a line style is chosen).

If autoscale is in effect, the ranges will be computed such that the plotted curve lies within the borders of the graph.

If autoscale is not in effect, and the smooth option is either `acspline` or `cspline`, the sampling of the generated curve is done across the intersection of the x range covered by the input data and the fixed abscissa range as defined by xrange.

If too few points are available to allow the selected option to be applied, an error message is produced. The minimum number is one for `unique` and `frequency`, four for `acsplines`, and three for the others.

The smooth options have no effect on function plots.

-- ACSPLINES --

The `acsplines` option approximates the data with a "natural smoothing spline". After the data are made monotonic in x (see `smooth unique`), a curve is piecewise constructed from segments of cubic polynomials whose coefficients are found by the weighting the data points; the weights are taken from the third column in the data file. That default can be modified by the third entry in the using list, e.g.,

 
      plot 'data-file' using 1:2:(1.0) smooth acsplines

Qualitatively, the absolute magnitude of the weights determines the number of segments used to construct the curve. If the weights are large, the effect of each datum is large and the curve approaches that produced by connecting consecutive points with natural cubic splines. If the weights are small, the curve is composed of fewer segments and thus is smoother; the limiting case is the single segment produced by a weighted linear least squares fit to all the data. The smoothing weight can be expressed in terms of errors as a statistical weight for a point divided by a "smoothing factor" for the curve so that (standard) errors in the file can be used as smoothing weights.

Example:

 
      sw(x,S)=1/(x*x*S)
      plot 'data_file' using 1:2:(sw($3,100)) smooth acsplines

-- BEZIER --

The `bezier` option approximates the data with a Bezier curve of degree n (the number of data points) that connects the endpoints.

-- CSPLINES --

The `csplines` option connects consecutive points by natural cubic splines after rendering the data monotonic (see `smooth unique`).

-- SBEZIER --

The `sbezier` option first renders the data monotonic (`unique`) and then applies the `bezier` algorithm.

-- UNIQUE --

The `unique` option makes the data monotonic in x; points with the same x-value are replaced by a single point having the average y-value. The resulting points are then connected by straight line segments. demos

-- FREQUENCY --

The `frequency` option makes the data monotonic in x; points with the same x-value are replaced by a single point having the summed y-values. The resulting points are then connected by straight line segments.


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2.12.1.7 special-filenames

A special filename of `'-'` specifies that the data are inline; i.e., they follow the command. Only the data follow the command; `plot` options like filters, titles, and line styles remain on the `plot` command line. This is similar to << in unix shell script, and $DECK in VMS DCL. The data are entered as though they are being read from a file, one data point per record. The letter "e" at the start of the first column terminates data entry. The using option can be applied to these data--using it to filter them through a function might make sense, but selecting columns probably doesn't!

`'-'` is intended for situations where it is useful to have data and commands together, e.g., when `gnuplot` is run as a sub-process of some front-end application. Some of the demos, for example, might use this feature. While `plot` options such as index and every are recognized, their use forces you to enter data that won't be used. For example, while

 
      plot '-' index 0, '-' index 1
      2
      4
      6

 
      10
      12
      14
      e
      2
      4
      6

 
      10
      12
      14
      e

does indeed work,

 
      plot '-', '-'
      2
      4
      6
      e
      10
      12
      14
      e

is a lot easier to type.

If you use `'-'` with replot, you may need to enter the data more than once (see replot).

A blank filename (") specifies that the previous filename should be reused. This can be useful with things like

 
      plot 'a/very/long/filename' using 1:2, '' using 1:3, '' using 1:4

(If you use both `'-'` and `"` on the same `plot` command, you'll need to have two sets of inline data, as in the example above.)

On some computer systems with a popen function (Unix), the datafile can be piped through a shell command by starting the file name with a '<'. For example,

 
      pop(x) = 103*exp(-x/10)
      plot "< awk '{print $1-1965, $2}' population.dat", pop(x)

would plot the same information as the first population example but with years since 1965 as the x axis. If you want to execute this example, you have to delete all comments from the data file above or substitute the following command for the first part of the command above (the part up to the comma):

 
      plot "< awk '$0 !~ /^#/ {print $1-1965, $2}' population.dat"

While this approach is most flexible, it is possible to achieve simple filtering with the using or thru keywords.


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2.12.1.8 thru

The thru function is provided for backward compatibility.

Syntax:

 
      plot 'file' thru f(x)

It is equivalent to:

 
      plot 'file' using 1:(f($2))

While the latter appears more complex, it is much more flexible. The more natural

 
      plot 'file' thru f(y)

also works (i.e. you can use y as the dummy variable).

thru is parsed for `splot` and `fit` but has no effect.


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2.12.1.9 using

The most common datafile modifier is using.

Syntax:

 
      plot 'file' using {<entry> {:<entry> {:<entry> ...}}} {'format'}

If a format is specified, each datafile record is read using the C library's 'scanf' function, with the specified format string. Otherwise the record is read and broken into columns at spaces or tabs. A format cannot be specified this way for time-format data (instead use `set xdata time`).

The resulting array of data is then sorted into columns according to the entries. Each <entry> may be a simple column number, which selects the datum, an expression enclosed in parentheses, or empty. The expression can use $1 to access the first item read, $2 for the second item, and so on. It can also use `column(x)` and `valid(x)` where x is an arbitrary expression resulting in an integer. `column(x)` returns the x'th datum; `valid(x)` tests that the datum in the x'th column is a valid number. A column number of 0 generates a number increasing (from zero) with each point, and is reset upon encountering two blank records. A column number of -1 gives the dataline number, which starts at 0, increments at single blank records, and is reset at double blank records. A column number of -2 gives the index number, which is incremented only when two blank records are found. An empty <entry> will default to its order in the list of entries. For example, `using ::4` is interpreted as `using 1:2:4`.

N.B.--the call command also uses $'s as a special character. See call for details about how to include a column number in a call argument list.

If the using list has but a single entry, that <entry> will be used for y and the data point number is used for x; for example, "`plot 'file' using 1`" is identical to "`plot 'file' using 0:1`". If the using list has two entries, these will be used for x and y. Additional entries are usually errors in x and/or y. See style for details about plotting styles that make use of error information, and `fit` for use of error information in curve fitting.

'scanf' accepts several numerical specifications but `gnuplot` requires all inputs to be double-precision floating-point variables, so "%lf" is essentially the only permissible specifier. A format string given by the user must contain at least one such input specifier, and no more than seven of them. 'scanf' expects to see white space--a blank, tab ("\t"), newline ("\n"), or formfeed ("\f")--between numbers; anything else in the input stream must be explicitly skipped.

Note that the use of "\t", "\n", or "\f" requires use of double-quotes rather than single-quotes.

Examples:

This creates a plot of the sum of the 2nd and 3rd data against the first: The format string specifies comma- rather than space-separated columns. The same result could be achieved by specifying `set datafile separator ","`.

 
      plot 'file' using 1:($2+$3) '%lf,%lf,%lf'

In this example the data are read from the file "MyData" using a more complicated format:

 
      plot 'MyData' using "%*lf%lf%*20[^\n]%lf"

The meaning of this format is:

 
      %*lf        ignore a number
      %lf         read a double-precision number (x by default)
      %*20[^\n]   ignore 20 non-newline characters
      %lf         read a double-precision number (y by default)

One trick is to use the ternary `?:` operator to filter data:

 
      plot 'file' using 1:($3>10 ? $2 : 1/0)

which plots the datum in column two against that in column one provided the datum in column three exceeds ten. `1/0` is undefined; `gnuplot` quietly ignores undefined points, so unsuitable points are suppressed.

In fact, you can use a constant expression for the column number, provided it doesn't start with an opening parenthesis; constructs like `using 0+(complicated expression)` can be used. The crucial point is that the expression is evaluated once if it doesn't start with a left parenthesis, or once for each data point read if it does.

If timeseries data are being used, the time can span multiple columns. The starting column should be specified. Note that the spaces within the time must be included when calculating starting columns for other data. E.g., if the first element on a line is a time with an embedded space, the y value should be specified as column three.

It should be noted that `plot 'file'`, `plot 'file' using 1:2`, and `plot 'file' using ($1):($2)` can be subtly different: 1) if file has some lines with one column and some with two, the first will invent x values when they are missing, the second will quietly ignore the lines with one column, and the third will store an undefined value for lines with one point (so that in a plot with lines, no line joins points across the bad point); 2) if a line contains text at the first column, the first will abort the plot on an error, but the second and third should quietly skip the garbage.

In fact, it is often possible to plot a file with lots of lines of garbage at the top simply by specifying

 
      plot 'file' using 1:2

However, if you want to leave text in your data files, it is safer to put the comment character (#) in the first column of the text lines. Feeble using demos.

If gnuplot is built with configuration option -enable-datastrings, then additional modifiers to using can specify handling of text fields in the datafile. See `datastrings`, `using xticlabels`, `using title`.

-- USING TITLE --

If gnuplot is built with configuration option -enable-datastrings, then the first entry of a column of the input data file can be used as a string to provide the plot title in the key box. The column containing specified is independent of the column[s] used for the plot itself.

 
   plot 'data' using 1:($2/$3) title column(N)

In this case the entry in the first row of column N will be used for the key entry of the plot constructed from dividing column 2 by column 3. The entry in the first row of columns 2 and 3 will be ignored.

-- XTICLABELS --

If gnuplot is built with configuration option -enable-datastrings, then a column of the input data file can be used to label axis tic marks. The format of such a plot command is

 
  plot 'datafile' using <xcol>:<ycol>:xticlabels(<labelcol>) with <plotstyle>

Tic labels may be read for any of the plot axes: x x2 y y2 z. The `ticlabels(<labelcol>)` specifiers must come after all of the data coordinate specifiers in the using portion of the command. For each data point which has a valid set of X,Y[,Z] coordinates, the text field found in column <labelcol> is added to the list of xtic labels at the same X coordinate as the point it belongs to. `xticlabels(<labelcol>)` may be shortened to `xtic(<labelcol>)`.

Example:

 
      splot "data" using 2:4:6:xtic(1):ytic(3):ztic(6)

In this example the x and y axis tic labels are taken from different columns than the x and y coordinate values. The z axis tics, however, are generated from the z coordinate of the corresponding point.

-- X2TICLABELS --

See `plot using xticlabels`.

-- YTICLABELS --

See `plot using xticlabels`.

-- Y2TICLABELS --

See `plot using xticlabels`.

-- ZTICLABELS --

See `plot using xticlabels`.


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2.12.2 errorbars

Error bars are supported for 2-d data file plots by reading one to four additional columns (or using entries); these additional values are used in different ways by the various errorbar styles.

In the default situation, `gnuplot` expects to see three, four, or six numbers on each line of the data file--either

 
      (x, y, ydelta),
      (x, y, ylow, yhigh),
      (x, y, xdelta),
      (x, y, xlow, xhigh),
      (x, y, xdelta, ydelta), or
      (x, y, xlow, xhigh, ylow, yhigh).

The x coordinate must be specified. The order of the numbers must be exactly as given above, though the using qualifier can manipulate the order and provide values for missing columns. For example,

 
      plot 'file' with errorbars
      plot 'file' using 1:2:(sqrt($1)) with xerrorbars
      plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars

The last example is for a file containing an unsupported combination of relative x and absolute y errors. The using entry generates absolute x min and max from the relative error.

The y error bar is a vertical line plotted from (x, ylow) to (x, yhigh). If ydelta is specified instead of ylow and yhigh, ylow = y - ydelta and yhigh = y + ydelta are derived. If there are only two numbers on the record, yhigh and ylow are both set to y. The x error bar is a horizontal line computed in the same fashion. To get lines plotted between the data points, `plot` the data file twice, once with errorbars and once with lines (but remember to use the `notitle` option on one to avoid two entries in the key). Alternately, use the errorlines command (see errorlines).

The error bars have crossbars at each end unless bars is used (see bars for details).

If autoscaling is on, the ranges will be adjusted to include the error bars.

See also errorbar demos.

See using, with, and style for more information.


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2.12.3 errorlines

Lines with error bars are supported for 2-d data file plots by reading one to four additional columns (or using entries); these additional values are used in different ways by the various errorlines styles.

In the default situation, `gnuplot` expects to see three, four, or six numbers on each line of the data file--either

 
      (x, y, ydelta),
      (x, y, ylow, yhigh),
      (x, y, xdelta),
      (x, y, xlow, xhigh),
      (x, y, xdelta, ydelta), or
      (x, y, xlow, xhigh, ylow, yhigh).

The x coordinate must be specified. The order of the numbers must be exactly as given above, though the using qualifier can manipulate the order and provide values for missing columns. For example,

 
      plot 'file' with errorlines
      plot 'file' using 1:2:(sqrt($1)) with xerrorlines
      plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorlines

The last example is for a file containing an unsupported combination of relative x and absolute y errors. The using entry generates absolute x min and max from the relative error.

The y error bar is a vertical line plotted from (x, ylow) to (x, yhigh). If ydelta is specified instead of ylow and yhigh, ylow = y - ydelta and yhigh = y + ydelta are derived. If there are only two numbers on the record, yhigh and ylow are both set to y. The x error bar is a horizontal line computed in the same fashion.

The error bars have crossbars at each end unless bars is used (see bars for details).

If autoscaling is on, the ranges will be adjusted to include the error bars.

See using, with, and style for more information.


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2.12.4 parametric

When in parametric mode (`set parametric`) mathematical expressions must be given in pairs for `plot` and in triplets for `splot`.

Examples:

 
      plot sin(t),t**2
      splot cos(u)*cos(v),cos(u)*sin(v),sin(u)

Data files are plotted as before, except any preceding parametric function must be fully specified before a data file is given as a plot. In other words, the x parametric function (`sin(t)` above) and the y parametric function (`t**2` above) must not be interrupted with any modifiers or data functions; doing so will generate a syntax error stating that the parametric function is not fully specified.

Other modifiers, such as with and `title`, may be specified only after the parametric function has been completed:

 
      plot sin(t),t**2 title 'Parametric example' with linespoints

See also Parametric Mode Demos.


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2.12.5 ranges

The optional ranges specify the region of the graph that will be displayed.

Syntax:

 
      [{<dummy-var>=}{{<min>}:{<max>}}]
      [{{<min>}:{<max>}}]

The first form applies to the independent variable (xrange or trange, if in parametric mode). The second form applies to the dependent variable yrange (and xrange, too, if in parametric mode). <dummy-var> is a new name for the independent variable. (The defaults may be changed with dummy.) The optional <min> and <max> terms can be constant expressions or *.

In non-parametric mode, the order in which ranges must be given is xrange and yrange.

In parametric mode, the order for the `plot` command is trange, xrange, and yrange. The following `plot` command shows setting the trange to [-pi:pi], the xrange to [-1.3:1.3] and the yrange to [-1:1] for the duration of the graph:

 
      plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2

Note that the x2range and y2range cannot be specified here--x2range and y2range must be used.

Ranges are interpreted in the order listed above for the appropriate mode. Once all those needed are specified, no further ones must be listed, but unneeded ones cannot be skipped--use an empty range `[]` as a placeholder.

`*` can be used to allow autoscaling of either of min and max. See also autoscale.

Ranges specified on the `plot` or `splot` command line affect only that graph; use the xrange, yrange, etc., commands to change the default ranges for future graphs.

With time data, you must provide the range (in the same manner as the time appears in the datafile) within quotes. `gnuplot` uses the timefmt string to read the value--see timefmt.

Examples:

This uses the current ranges:

 
      plot cos(x)

This sets the x range only:

 
      plot [-10:30] sin(pi*x)/(pi*x)

This is the same, but uses t as the dummy-variable:

 
      plot [t = -10 :30]  sin(pi*t)/(pi*t)

This sets both the x and y ranges:

 
      plot [-pi:pi] [-3:3]  tan(x), 1/x

This sets only the y range, and turns off autoscaling on both axes:

 
      plot [ ] [-2:sin(5)*-8] sin(x)**besj0(x)

This sets xmax and ymin only:

 
      plot [:200] [-pi:]  exp(sin(x))

This sets the x range for a timeseries:

 
      set timefmt "%d/%m/%y %H:%M"
      plot ["1/6/93 12:00":"5/6/93 12:00"] 'timedata.dat'


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2.12.6 title

A line title for each function and data set appears in the key, accompanied by a sample of the line and/or symbol used to represent it. It can be changed by using the `title` option.

Syntax:

 
      title "<title>" | notitle ["<ignored title>"]

where <title> is the new title of the line and must be enclosed in quotes. The quotes will not be shown in the key. A special character may be given as a backslash followed by its octal value ("\345"). The tab character "\t" is understood. Note that backslash processing occurs only for strings enclosed in double quotes--use single quotes to prevent such processing. The newline character "\n" is not processed in key entries in either type of string.

The line title and sample can be omitted from the key by using the keyword `notitle`. A null title (`title "`) is equivalent to `notitle`. If only the sample is wanted, use one or more blanks (`title ' '`). If `notitle` is followed by a string this string is ignored.

If `key autotitles` is set (which is the default) and neither `title` nor `notitle` are specified the line title is the function name or the file name as it appears on the `plot` command. If it is a file name, any datafile modifiers specified will be included in the default title.

The layout of the key itself (position, title justification, etc.) can be controlled by key. Please see key for details.

Examples:

This plots y=x with the title 'x':

 
      plot x

This plots x squared with title "x^2" and file "data.1" with title "measured data":

 
      plot x**2 title "x^2", 'data.1' t "measured data"

This puts an untitled circular border around a polar graph:

 
      set polar; plot my_function(t), 1 notitle


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2.12.7 with

Functions and data may be displayed in one of a large number of styles. The with keyword provides the means of selection.

Syntax:

 
      with <style> { {linestyle | ls <line_style>}
                     | {{linetype  | lt <line_type>}
                        {linewidth | lw <line_width>}
                        {linecolor | lc <colorspec>}
                        {pointtype | pt <point_type>}
                        {pointsize | ps <point_size>}
                        {fill | fs <fillstyle>}
                        {nohidden3d}
                        {palette}}
                   }

where <style> is either `lines`, `points`, `linespoints`, `impulses`, `dots`, `steps`, `fsteps`, `histeps`, errorbars, `labels`, `xerrorbars`, `yerrorbars`, `xyerrorbars`, errorlines, `xerrorlines`, `yerrorlines`, `xyerrorlines`, `boxes`, `histograms`, `filledcurves`, `boxerrorbars`, `boxxyerrorbars`, `financebars`, `candlesticks`, `vectors`, `image`, `rgbimage` or pm3d. Some of these styles require additional information. See `plotting styles` for details of each style. `fill` is relevant only to certain 2D plots (currently `boxes` `boxxyerrorbars` and `candlesticks`). Note that `filledcurves` and pm3d can take an additional option not listed above (the latter only when used in the `splot` command)--see their help or examples below for more details.

Default styles are chosen with the `set style function` and `set style data` commands.

By default, each function and data file will use a different line type and point type, up to the maximum number of available types. All terminal drivers support at least six different point types, and re-use them, in order, if more are required. The LaTeX driver supplies an additional six point types (all variants of a circle), and thus will only repeat after 12 curves are plotted with points. The PostScript drivers (postscript) supplies a total of 64.

If you wish to choose the line or point type for a single plot, <line_type> and <point_type> may be specified. These are positive integer constants (or expressions) that specify the line type and point type to be used for the plot. Use test to display the types available for your terminal.

You may also scale the line width and point size for a plot by using <line_width> and <point_size>, which are specified relative to the default values for each terminal. The pointsize may also be altered globally--see pointsize for details. But note that both <point_size> as set here and as set by pointsize multiply the default point size--their effects are not cumulative. That is, `set pointsize 2; plot x w p ps 3` will use points three times default size, not six.

It is also possible to specify `pointsize variable` either as part of a line style or for an individual plot. In this case one extra column of input is required, i.e. 3 columns for a 2D plot and 4 columns for a 3D splot. The size of each individual point is determined by multiplying the global pointsize by the value read from the data file.

If you have defined specific line type/width and point type/size combinations with `set style line`, one of these may be selected by setting <line_style> to the index of the desired style.

If gnuplot was built with pm3d support, the special keyword palette is allowed for smooth color change of lines, points and dots in `splots`. The color is chosen from a smooth palette which was set previously with the command palette. The color value corresponds to the z-value of the point coordinates or to the color coordinate if specified by the 4th parameter in using. Both 2d and 3d plots (`plot` and `splot` commands) can use palette colors as specified by either their fractional value or the corresponding value mapped to the colorbox range. 2d plots can not use palette colors mapped by Z value. See `colors`, palette, `linetype`.

The keyword `nohidden3d` applies only to plots made with the `splot` command. Normally the global option hidden3d applies to all plots in the graph. You can attach the `nohidden3d` option to any individual plots that you want to exclude from the hidden3d processing. The individual elements other than surfaces (i.e. lines, dots, labels, ...) of a plot marked `nohidden3d` will all be drawn, even if they would normally be obscured by other plot elements.

The keywords may be abbreviated as indicated.

Note that the `linewidth`, pointsize and palette options are not supported by all terminals.

Examples:

This plots sin(x) with impulses:

 
      plot sin(x) with impulses

This plots x with points, x**2 with the default:

 
      plot x w points, x**2

This plots tan(x) with the default function style, file "data.1" with lines:

 
      plot [ ] [-2:5] tan(x), 'data.1' with l

This plots "leastsq.dat" with impulses:

 
      plot 'leastsq.dat' w i

This plots the data file "population" with boxes:

 
      plot 'population' with boxes

This plots "exper.dat" with errorbars and lines connecting the points (errorbars require three or four columns):

 
      plot 'exper.dat' w lines, 'exper.dat' notitle w errorbars

Another way to plot "exper.dat" with errorlines (errorbars require three or four columns):

 
      plot 'exper.dat' w errorlines

This plots sin(x) and cos(x) with linespoints, using the same line type but different point types:

 
      plot sin(x) with linesp lt 1 pt 3, cos(x) with linesp lt 1 pt 4

This plots file "data" with points of type 3 and twice usual size:

 
      plot 'data' with points pointtype 3 pointsize 2

This plots file "data" with variable pointsize read from column 4

 
      plot 'data' using 1:2:4 with points pt 5 pointsize variable

This plots two data sets with lines differing only by weight:

 
      plot 'd1' t "good" w l lt 2 lw 3, 'd2' t "bad" w l lt 2 lw 1

This plots filled curve of x*x and a color stripe:

 
      plot x*x with filledcurve closed, 40 with filledcurve y1=10

This plots x*x and a color box:

 
      plot x*x, (x>=-5 && x<=5 ? 40 : 1/0) with filledcurve y1=10 lt 8

This plots a surface with color lines:

 
      splot x*x-y*y with line palette

This plots two color surfaces at different altitudes:

 
      splot x*x-y*y with pm3d, x*x+y*y with pm3d at t


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2.13 print

The `print` command prints the value of <expression> to the screen. It is synonymous with `pause 0`. <expression> may be anything that `gnuplot` can evaluate that produces a number, or it can be a string.

Syntax:

 
      print <expression> {, <expression>, ...}

See `expressions`. The output file can be set with `set print`.


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2.14 pwd

The pwd command prints the name of the working directory to the screen.


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2.15 quit

The exit and quit commands and END-OF-FILE character will exit `gnuplot`. Each of these commands will clear the output device (as does the clear command) before exiting.


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2.16 raise

Syntax:

 
      raise {plot_window_nb}

The raise command raises (opposite to lower) plot window(s) associated with the interactive terminal of your gnuplot session, i.e. `pm`, `win`, `wxt` or `x11`. It puts the plot window to front (top) in the z-order windows stack of the window manager of your desktop.

As `x11` and `wxt` support multiple plot windows, then by default they raise these windows in descending order of most recently created on top to the least recently created on bottom. If a plot number is supplied as an optional parameter, only the associated plot window will be raised if it exists.

The optional parameter is ignored for single plot-windows terminal, i.e. `pm` and `win`.

 
 If the window is not raised under X11, then (1) they don't run in the same
 X11 session (telnet or ssh session, for example), or (2) raising is blocked
 by your window manager. On KDE, you may like to go to the KDE Control Center
 => Desktop => Window Behaviour => Advanced and set the "Focus stealing
 prevention level" to None (default is Low).


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2.17 replot

The replot command without arguments repeats the last `plot` or `splot` command. This can be useful for viewing a plot with different `set` options, or when generating the same plot for several devices.

Arguments specified after a replot command will be added onto the last `plot` or `splot` command (with an implied ',' separator) before it is repeated. replot accepts the same arguments as the `plot` and `splot` commands except that ranges cannot be specified. Thus you can use replot to plot a function against the second axes if the previous command was `plot` but not if it was `splot`.

N.B.--use of

 
      plot '-' ; ... ; replot

is not recommended. `gnuplot` does not store the inline data internally, so since replot appends new information to the previous `plot` and then executes the modified command, the `'-'` from the initial `plot` will expect to read inline data again.

Note that replot does not work in multiplot mode, since it reproduces only the last plot rather than the entire screen.

See also `command-line-editing` for ways to edit the last `plot` (`splot`) command.

See also `show plot` to show the whole current plotting command, and the possibility to copy it into the `history`.


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2.18 reread

The reread command causes the current `gnuplot` command file, as specified by a `load` command or on the command line, to be reset to its starting point before further commands are read from it. This essentially implements an endless loop of the commands from the beginning of the command file to the reread command. (But this is not necessarily a disaster--reread can be very useful when used in conjunction with if. See if for details.) The reread command has no effect if input from standard input.

Examples:

Suppose the file "looper" contains the commands

 
      a=a+1
      plot sin(x*a)
      pause -1
      if(a<5) reread

and from within `gnuplot` you submit the commands

 
      a=0
      load 'looper'

The result will be four plots (separated by the pause message).

Suppose the file "data" contains six columns of numbers with a total yrange from 0 to 10; the first is x and the next are five different functions of x. Suppose also that the file "plotter" contains the commands

 
      c_p = c_p+1
      plot "$0" using 1:c_p with lines linetype c_p
      if(c_p <  n_p) reread

and from within `gnuplot` you submit the commands

 
      n_p=6
      c_p=1
      unset key
      set yrange [0:10]
      set multiplot
      call 'plotter' 'data'
      unset multiplot

The result is a single graph consisting of five plots. The yrange must be set explicitly to guarantee that the five separate graphs (drawn on top of each other in multiplot mode) will have exactly the same axes. The linetype must be specified; otherwise all the plots would be drawn with the same type. See animate.dem in demo directory for an animated example.


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2.19 reset

The reset command causes all graph-related options that can be set with the `set` command to take on their default values. This command is useful, e.g., to restore the default graph settings at the end of a command file, or to return to a defined state after lots of settings have been changed within a command file. Please refer to the `set` command to see the default values that the various options take.

The following `set` commands do not change the graph status and are thus left unchanged: the terminal set with `set term`, the output file set with output and directory paths set with loadpath and fontpath.


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2.20 save

The save command saves user-defined functions, variables, the `set term` status, all `set` options, or all of these, plus the last `plot` (`splot`) command to the specified file.

Syntax:

 
      save  {<option>} '<filename>'

where <option> is `functions`, variables, `terminal` or `set`. If no option is used, `gnuplot` saves functions, variables, `set` options and the last `plot` (`splot`) command.

saved files are written in text format and may be read by the `load` command. For save with the `set` option or without any option, the `terminal` choice and the output filename are written out as a comment, to get an output file that works in other installations of gnuplot, without changes and without risk of unwillingly overwriting files.

`save terminal` will write out just the `terminal` status, without the comment marker in front of it. This is mainly useful for switching the `terminal` setting for a short while, and getting back to the previously set terminal, afterwards, by loading the saved `terminal` status. Note that for a single gnuplot session you may rather use the other method of saving and restoring current terminal by the commands `set term push` and `set term pop`, see `set term`.

The filename must be enclosed in quotes.

The special filename "-" may be used to save commands to standard output. On systems which support a popen function (Unix), the output of save can be piped through an external program by starting the file name with a '|'. This provides a consistent interface to `gnuplot`'s internal settings to programs which communicate with `gnuplot` through a pipe. Please see help for `batch/interactive` for more details.

Examples:

 
      save 'work.gnu'
      save functions 'func.dat'
      save var 'var.dat'
      save set 'options.dat'
      save term 'myterm.gnu'
      save '-'
      save '|grep title >t.gp'


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2.21 set-show

The `set` command can be used to set _lots_ of options. No screen is drawn, however, until a `plot`, `splot`, or replot command is given.

The `show` command shows their settings; `show all` shows all the settings.

Options changed using `set` can be returned to the default state by giving the corresponding unset command. See also the reset command, which returns all settable parameters to default values.

If a variable contains time/date data, `show` will display it according to the format currently defined by timefmt, even if that was not in effect when the variable was initially defined.


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2.21.1 angles

By default, `gnuplot` assumes the independent variable in polar graphs is in units of radians. If `set angles degrees` is specified before `set polar`, then the default range is [0:360] and the independent variable has units of degrees. This is particularly useful for plots of data files. The angle setting also applies to 3-d mapping as set via the mapping command.

Syntax:

 
      set angles {degrees | radians}
      show angles

The angle specified in `set grid polar` is also read and displayed in the units specified by angles.

angles also affects the arguments of the machine-defined functions sin(x), cos(x) and tan(x), and the outputs of asin(x), acos(x), atan(x), atan2(x), and arg(x). It has no effect on the arguments of hyperbolic functions or Bessel functions. However, the output arguments of inverse hyperbolic functions of complex arguments are affected; if these functions are used, `set angles radians` must be in effect to maintain consistency between input and output arguments.

 
      x={1.0,0.1}
      set angles radians
      y=sinh(x)
      print y         #prints {1.16933, 0.154051}
      print asinh(y)  #prints {1.0, 0.1}

but

 
      set angles degrees
      y=sinh(x)
      print y         #prints {1.16933, 0.154051}
      print asinh(y)  #prints {57.29578, 5.729578}

See also poldat.dem: polar plot using angles demo.


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2.21.2 arrow

Arbitrary arrows can be placed on a plot using the arrow command.

Syntax:

 
      set arrow {<tag>} {from <position>} {to|rto <position>}
                { {arrowstyle | as <arrow_style>}
                  | { {nohead | head | backhead | heads}
                      {size <length>,<angle>{,<backangle>}}
                      {filled | empty | nofilled}
                      {front | back}
                      { {linestyle | ls <line_style>}
                        | {linetype | lt <line_type>}
                          {linewidth | lw <line_width} } } }

 
      unset arrow {<tag>}
      show arrow {<tag>}

<tag> is an integer that identifies the arrow. If no tag is given, the lowest unused tag value is assigned automatically. The tag can be used to delete or change a specific arrow. To change any attribute of an existing arrow, use the arrow command with the appropriate tag and specify the parts of the arrow to be changed.

The <position>s are specified by either x,y or x,y,z, and may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. Unspecified coordinates default to 0. The end points can be specified in one of five coordinate systems--`first` or `second` axes, `graph`, `screen`, or `character`. See `coordinates` for details. A coordinate system specifier does not carry over from the "from" position to the "to" position. Arrows outside the screen boundaries are permitted but may cause device errors. If the end point is specified by "rto" instead of "to" it is drawn relatively to the start point. For linear axes, `graph` and `screen` coordinates, the distance between the start and the end point corresponds to the given relative coordinate. For logarithmic axes, the relative given coordinate corresponds to the factor of the coordinate between start and end point. Thus, a negative relative value or zero are not allowed for logarithmic axes.

Specifying `nohead` produces an arrow drawn without a head--a line segment. This gives you yet another way to draw a line segment on the plot. By default, an arrow has a head at its end. Specifying `backhead` draws an arrow head at the start point of the arrow while `heads` draws arrow heads on both ends of the line. Not all terminal types support double-ended arrows.

Head size can be controlled by `size <length>,<angle>` or `size <length>,<angle>,<backangle>`, where `<length>` defines length of each branch of the arrow head and `<angle>` the angle (in degrees) they make with the arrow. `<Length>` is in x-axis units; this can be changed by `first`, `second`, `graph`, `screen`, or `character` before the <length>; see `coordinates` for details. `<Backangle>` only takes effect when `filled` or `empty` is also used. Then, `<backangle>` is the angle (in degrees) the back branches make with the arrow (in the same direction as `<angle>`). The `fig` terminal has a restricted backangle function. It supports three different angles. There are two thresholds: Below 70 degrees, the arrow head gets an indented back angle. Above 110 degrees, the arrow head has an acute back angle. Between these thresholds, the back line is straight.

Specifying `filled` produces filled arrow heads (if heads are used). Filling is supported on filled-polygon capable terminals, see help of pm3d for their list, otherwise the arrow heads are closed but not filled. The same result (closed but not filled arrow head) is reached by specifying `empty`. Further, filling and outline is obviously not supported on terminals drawing arrows by their own specific routines, like `metafont`, `metapost`, `latex` or `tgif`.

The line style may be selected from a user-defined list of line styles (see `set style line`) or may be defined here by providing values for <line_type> (an index from the default list of styles) and/or <line_width> (which is a multiplier for the default width).

Note, however, that if a user-defined line style has been selected, its properties (type and width) cannot be altered merely by issuing another arrow command with the appropriate index and `lt` or `lw`.

If `front` is given, the arrow is written on top of the graphed data. If `back` is given (the default), the arrow is written underneath the graphed data. Using `front` will prevent an arrow from being obscured by dense data.

Examples:

To set an arrow pointing from the origin to (1,2) with user-defined style 5, use:

 
      set arrow to 1,2 ls 5

To set an arrow from bottom left of plotting area to (-5,5,3), and tag the arrow number 3, use:

 
      set arrow 3 from graph 0,0 to -5,5,3

To change the preceding arrow to end at 1,1,1, without an arrow head and double its width, use:

 
      set arrow 3 to 1,1,1 nohead lw 2

To draw a vertical line from the bottom to the top of the graph at x=3, use:

 
      set arrow from 3, graph 0 to 3, graph 1 nohead

To draw a vertical arrow with T-shape ends, use:

 
      set arrow 3 from 0,-5 to 0,5 heads size screen 0.1,90

To draw an arrow relatively to the start point, where the relative distances are given in graph coordinates, use:

 
      set arrow from 0,-5 rto graph 0.1,0.1

To draw an arrow with relative end point in logarithmic x axis, use:

 
      set logscale x
      set arrow from 100,-5 rto 10,10

This draws an arrow from 100,-5 to 1000,5. For the logarithmic x axis, the relative coordinate 10 means "factor 10" while for the linear y axis, the relative coordinate 10 means "difference 10".

To delete arrow number 2, use:

 
      unset arrow 2

To delete all arrows, use:

 
      unset arrow

To show all arrows (in tag order), use:

 
      show arrow

arrows demos.


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2.21.3 autoscale

Autoscaling may be set individually on the x, y or z axis or globally on all axes. The default is to autoscale all axes.

Syntax:

 
      set autoscale {<axes>{|min|max|fixmin|fixmax|fix} | fix | keepfix}
      unset autoscale {<axes>}
      show autoscale

where <axes> is either `x`, `y`, `z`, `cb`, `x2`, `y2` or `xy`. A keyword with `min` or `max` appended (this cannot be done with `xy`) tells `gnuplot` to autoscale just the minimum or maximum of that axis. If no keyword is given, all axes are autoscaled.

A keyword with `fixmin`, `fixmax` or `fix` appended tells gnuplot to disable extension of the axis range to the next tic mark position, for autoscaled axes using equidistant tics; `set autoscale fix` sets this for all axes. Command `set autoscale keepfix` autoscales all axes while keeping the fix settings.

When autoscaling, the axis range is automatically computed and the dependent axis (y for a `plot` and z for `splot`) is scaled to include the range of the function or data being plotted.

If autoscaling of the dependent axis (y or z) is not set, the current y or z range is used.

Autoscaling the independent variables (x for `plot` and x,y for `splot`) is a request to set the domain to match any data file being plotted. If there are no data files, autoscaling an independent variable has no effect. In other words, in the absence of a data file, functions alone do not affect the x range (or the y range if plotting z = f(x,y)).

Please see xrange for additional information about ranges.

The behavior of autoscaling remains consistent in parametric mode, (see `set parametric`). However, there are more dependent variables and hence more control over x, y, and z axis scales. In parametric mode, the independent or dummy variable is t for `plot`s and u,v for `splot`s. autoscale in parametric mode, then, controls all ranges (t, u, v, x, y, and z) and allows x, y, and z to be fully autoscaled.

Autoscaling works the same way for polar mode as it does for parametric mode for `plot`, with the extension that in polar mode dummy can be used to change the independent variable from t (see dummy).

When tics are displayed on second axes but no plot has been specified for those axes, x2range and y2range are inherited from xrange and yrange. This is done _before_ xrange and yrange are autoextended to a whole number of tics, which can cause unexpected results. You can use the `fixmin` or `fixmax` options to avoid this.

Examples:

This sets autoscaling of the y axis (other axes are not affected):

 
      set autoscale y

This sets autoscaling only for the minimum of the y axis (the maximum of the y axis and the other axes are not affected):

 
      set autoscale ymin

This disables extension of the x2 axis tics to the next tic mark, thus keeping the exact range as found in the plotted data and functions:

 
      set autoscale x2fixmin
      set autoscale x2fixmax

This sets autoscaling of the x and y axes:

 
      set autoscale xy

This sets autoscaling of the x, y, z, x2 and y2 axes:

 
      set autoscale

This disables autoscaling of the x, y, z, x2 and y2 axes:

 
      unset autoscale

This disables autoscaling of the z axis only:

 
      unset autoscale z


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2.21.3.1 parametric mode

When in parametric mode (`set parametric`), the xrange is as fully scalable as the y range. In other words, in parametric mode the x axis can be automatically scaled to fit the range of the parametric function that is being plotted. Of course, the y axis can also be automatically scaled just as in the non-parametric case. If autoscaling on the x axis is not set, the current x range is used.

Data files are plotted the same in parametric and non-parametric mode. However, there is a difference in mixed function and data plots: in non-parametric mode with autoscaled x, the x range of the datafile controls the x range of the functions; in parametric mode it has no influence.

For completeness a last command `set autoscale t` is accepted. However, the effect of this "scaling" is very minor. When `gnuplot` determines that the t range would be empty, it makes a small adjustment if autoscaling is true. Otherwise, `gnuplot` gives an error. Such behavior may, in fact, not be very useful and the command `set autoscale t` is certainly questionable.

`splot` extends the above ideas as you would expect. If autoscaling is set, then x, y, and z ranges are computed and each axis scaled to fit the resulting data.


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2.21.3.2 polar mode

When in polar mode (`set polar`), the xrange and the yrange are both found from the polar coordinates, and thus they can both be automatically scaled. In other words, in polar mode both the x and y axes can be automatically scaled to fit the ranges of the polar function that is being plotted.

When plotting functions in polar mode, the rrange may be autoscaled. When plotting data files in polar mode, the trange may also be autoscaled. Note that if the trange is contained within one quadrant, autoscaling will produce a polar plot of only that single quadrant.

Explicitly setting one or two ranges but not others may lead to unexpected results. See also polar demos.


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2.21.4 bars

The bars command controls the tics at the ends of error bars, and also the width of the boxes in plot styles candlesticks and financebars.

Syntax:

 
      set bars {small | large | fullwidth | <size>}
      unset bars
      show bars

`small` is a synonym for 0.0, and `large` for 1.0. The default is 1.0 if no size is given.

The keyword `fullwidth` is relevant only to histograms with errorbars. It sets the width of the errorbar ends to be the same as the width of the associated box in the histogram. It does not change the width of the box itself.


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2.21.5 bmargin

The command bmargin sets the size of the bottom margin. Please see margin for details.


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2.21.6 border

The border and border commands control the display of the graph borders for the `plot` and `splot` commands. Note that the borders do not necessarily coincide with the axes; with `plot` they often do, but with `splot` they usually do not.

Syntax:

 
      set border {<integer>} {front | back} {linewidth | lw <line_width>}
                 {{linestyle | ls <line_style>} | {linetype | lt <line_type>}}
      unset border
      show border

With a `splot` displayed in an arbitrary orientation, like `set view 56,103`, the four corners of the x-y plane can be referred to as "front", "back", "left" and "right". A similar set of four corners exist for the top surface, of course. Thus the border connecting, say, the back and right corners of the x-y plane is the "bottom right back" border, and the border connecting the top and bottom front corners is the "front vertical". (This nomenclature is defined solely to allow the reader to figure out the table that follows.)

The borders are encoded in a 12-bit integer: the bottom four bits control the border for `plot` and the sides of the base for `splot`; the next four bits control the verticals in `splot`; the top four bits control the edges on top of the `splot`. In detail, `<integer>` should be the sum of the appropriate entries from the following table:

 
            Bit     plot        splot
              1   bottom      bottom left front
              2   left        bottom left back
              4   top         bottom right front
              8   right       bottom right back
             16   no effect   left vertical
             32   no effect   back vertical
             64   no effect   right vertical
            128   no effect   front vertical
            256   no effect   top left back
            512   no effect   top right back
           1024   no effect   top left front
           2048   no effect   top right front

Various bits or combinations of bits may be added together in the command.

The default is 31, which is all four sides for `plot`, and base and z axis for `splot`.

In 2D plots the border is normally drawn on top of all plots elements (`front`). If you want the border to be drawn behind the plot elements, use `set border back`.

Using the optional <line_style>, <line_type> and <line_width> specifiers, the way the border lines are drawn can be influenced (limited by what the current terminal driver supports).

For `plot`, tics may be drawn on edges other than bottom and left by enabling the second axes - see xtics for details.

If a `splot` draws only on the base, as is the case with "`unset surface; set contour base`", then the verticals and the top are not drawn even if they are specified.

The `set grid` options 'back', 'front' and 'layerdefault' also control the order in which the border lines are drawn with respect to the output of the plotted data.

Examples:

Draw default borders:

 
      set border

Draw only the left and bottom (`plot`) or both front and back bottom left (`splot`) borders:

 
      set border 3

Draw a complete box around a `splot`:

 
      set border 4095

Draw a topless box around a `splot`, omitting the front vertical:

 
      set border 127+256+512 # or set border 1023-128

Draw only the top and right borders for a `plot` and label them as axes:

 
      unset xtics; unset ytics; set x2tics; set y2tics; set border 12


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2.21.7 boxwidth

The boxwidth command is used to set the default width of boxes in the `boxes`, `boxerrorbars`, `candlesticks` and `histograms` styles.

Syntax:

 
      set boxwidth {<width>} {absolute|relative}
      show boxwidth

By default, adjacent boxes are extended in width until they touch each other. A different default width may be specified using the boxwidth command. `Relative` widths are interpreted as being a fraction of this default width.

An explicit value for the boxwidth is interpreted as being a number of units along the current x axis (`absolute`) unless the modifier `relative` is given. If the x axis is a log-scale (see `set log`) then the value of boxwidth is truly "absolute" only at x=1; this physical width is maintained everywhere along the axis (i.e. the boxes do not become narrower the value of x increases). If the range spanned by a log scale x axis is far from x=1, some experimentation may be required to find a useful value of boxwidth.

The default is superseded by explicit width information taken from an extra data column in styles `boxes` or `boxerrorbars`. In a four-column data set, the fourth column will be interpreted as the box width unless the width is set to -2.0, in which case the width will be calculated automatically. See `style boxes` and `style boxerrorbars` for more details.

To set the box width to automatic use the command

 
      set boxwidth

or, for four-column data,

 
      set boxwidth -2

The same effect can be achieved with the using keyword in `plot`:

 
      plot 'file' using 1:2:3:4:(-2)

To set the box width to half of the automatic size use

 
      set boxwidth 0.5 relative

To set the box width to an absolute value of 2 use

 
      set boxwidth 2 absolute


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2.21.8 clabel

`gnuplot` will vary the linetype used for each contour level when clabel is set. When this option on (the default), a legend labels each linestyle with the z level it represents. It is not possible at present to separate the contour labels from the surface key.

Syntax:

 
      set clabel {'<format>'}
      unset clabel
      show clabel

The default for the format string is %8.3g, which gives three decimal places. This may produce poor label alignment if the key is altered from its default configuration.

The first contour linetype, or only contour linetype when clabel is off, is the surface linetype +1; contour points are the same style as surface points.

See also contour.


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2.21.9 clip

`gnuplot` can clip data points and lines that are near the boundaries of a graph.

Syntax:

 
      set clip <clip-type>
      unset clip <clip-type>
      show clip

Three clip types for points and lines are supported by `gnuplot`: `points`, `one`, and `two`. One, two, or all three clip types may be active for a single graph. Note that clipping of color filled quadrangles drawn by pm3d maps and surfaces is not controlled by this command, but by `set pm3d clip1in` and `set pm3d clip4in`.

The `points` clip type forces `gnuplot` to clip (actually, not plot at all) data points that fall within but too close to the boundaries. This is done so that large symbols used for points will not extend outside the boundary lines. Without clipping points near the boundaries, the plot may look bad. Adjusting the x and y ranges may give similar results.

Setting the `one` clip type causes `gnuplot` to draw a line segment which has only one of its two endpoints within the graph. Only the in-range portion of the line is drawn. The alternative is to not draw any portion of the line segment.

Some lines may have both endpoints out of range, but pass through the graph. Setting the `two` clip-type allows the visible portion of these lines to be drawn.

In no case is a line drawn outside the graph.

The defaults are `noclip points`, `clip one`, and `noclip two`.

To check the state of all forms of clipping, use

 
      show clip

For backward compatibility with older versions, the following forms are also permitted:

 
      set clip
      unset clip

clip is synonymous with `set clip points`; clip turns off all three types of clipping.


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2.21.10 cntrparam

cntrparam controls the generation of contours and their smoothness for a contour plot. contour displays current settings of cntrparam as well as contour.

Syntax:

 
      set cntrparam { { linear
                      | cubicspline
                      | bspline
                      | points <n>
                      | order <n>
                      | levels { auto {<n>} | <n>
                                 | discrete <z1> {,<z2>{,<z3>...}}
                                 | incremental <start>, <incr> {,<end>}
                               }
                      }
                    }
      show contour

This command has two functions. First, it sets the values of z for which contour points are to be determined (by linear interpolation between data points or function isosamples.) Second, it controls the way contours are drawn between the points determined to be of equal z. <n> should be an integral constant expression and <z1>, <z2> ... any constant expressions. The parameters are:

`linear`, `cubicspline`, `bspline`--Controls type of approximation or interpolation. If `linear`, then straight line segments connect points of equal z magnitude. If `cubicspline`, then piecewise-linear contours are interpolated between the same equal z points to form somewhat smoother contours, but which may undulate. If `bspline`, a guaranteed-smoother curve is drawn, which only approximates the position of the points of equal-z.

`points`--Eventually all drawings are done with piecewise-linear strokes. This number controls the number of line segments used to approximate the `bspline` or `cubicspline` curve. Number of cubicspline or bspline segments (strokes) = `points` * number of linear segments.

`order`--Order of the bspline approximation to be used. The bigger this order is, the smoother the resulting contour. (Of course, higher order bspline curves will move further away from the original piecewise linear data.) This option is relevant for `bspline` mode only. Allowed values are integers in the range from 2 (linear) to 10.

`levels`-- Selection of contour levels, controlled by `auto` (default), `discrete`, `incremental`, and <n>, number of contour levels.

For `auto`, <n> specifies a nominal number of levels; the actual number will be adjusted to give simple labels. If the surface is bounded by zmin and zmax, contours will be generated at integer multiples of dz between zmin and zmax, where dz is 1, 2, or 5 times some power of ten (like the step between two tic marks).

For `levels discrete`, contours will be generated at z = <z1>, <z2> ... as specified; the number of discrete levels sets the number of contour levels. In `discrete` mode, any `set cntrparam levels <n>` are ignored.

For `incremental`, contours are generated at values of z beginning at <start> and increasing by <increment>, until the number of contours is reached. <end> is used to determine the number of contour levels, which will be changed by any subsequent `set cntrparam levels <n>`. If the z axis is logarithmic, <increment> will be interpreted as a factor, just like in ztics.

If the command cntrparam is given without any arguments specified, the defaults are used: linear, 5 points, order 4, 5 auto levels.

Examples:

 
      set cntrparam bspline
      set cntrparam points 7
      set cntrparam order 10

To select levels automatically, 5 if the level increment criteria are met:

 
      set cntrparam levels auto 5

To specify discrete levels at .1, .37, and .9:

 
      set cntrparam levels discrete .1,1/exp(1),.9

To specify levels from 0 to 4 with increment 1:

 
      set cntrparam levels incremental  0,1,4

To set the number of levels to 10 (changing an incremental end or possibly the number of auto levels):

 
      set cntrparam levels 10

To set the start and increment while retaining the number of levels:

 
      set cntrparam levels incremental 100,50

See also contour for control of where the contours are drawn, and clabel for control of the format of the contour labels and linetypes.

See also contours demo (contours.dem) and contours with user defined levels demo (discrete.dem).


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2.21.11 color box

The color scheme, i.e. the gradient of the smooth color with min_z and max_z values of pm3d's palette, is drawn in a color box unless `unset colorbox`.

 
      set colorbox
      set colorbox {
                 { vertical | horizontal }
                 { default | user }
                 { origin x, y }
                 { size x, y }
                 { noborder | bdefault | border [line style] }
               }
      show colorbox
      unset colorbox

Colorbox position can be `default` or `user`. If the latter is specified the values as given with the origin and size subcommands are used.

`vertical` and `horizontal` switches the orientation of the color gradient.

`origin x, y` and `size x, y` are used only in combination with the `user` option. The x and y values are interpreted as screen coordinates by default, and this is the only legal option for 3D plots. 2D plots, including splot with `set view map`, allow any coordinate system to be specified. Try for example:

 
    set colorbox horiz user origin .1,.02 size .8,.04

which will draw a horizontal gradient somewhere at the bottom of the graph.

border turns the border on (this is the default). `noborder` turns the border off. If an positive integer argument is given after border, it is used as a line style tag which is used for drawing the border, e.g.:

 
    set style line 2604 linetype -1 linewidth .4
    set colorbox border 2604

will use line style `2604`, a thin line with the default border color (-1) for drawing the border. `bdefault` (which is the default) will use the default border line style for drawing the border of the color box.

The axis of the color box is called `cb` and it is controlled by means of the usual axes commands, i.e. `set/unset/show` with cbrange, `[m]cbtics`, `format cb`, `grid [m]cb`, cblabel, and perhaps even cbdata, `[no]cbdtics`, `[no]cbmtics`.

`set colorbox` without any parameter switches the position to default. `unset colorbox` resets the default parameters for the colorbox and switches the colorbox off.

See also help for pm3d, palette, pm3d, and `set style line`.


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2.21.12 contour

contour enables contour drawing for surfaces. This option is available for `splot` only. It requires grid data, see `grid_data` for more details. If contours are desired from non-grid data, dgrid3d can be used to create an appropriate grid.

Syntax:

 
      set contour {base | surface | both}
      unset contour
      show contour

The three options specify where to draw the contours: `base` draws the contours on the grid base where the x/ytics are placed, surface draws the contours on the surfaces themselves, and `both` draws the contours on both the base and the surface. If no option is provided, the default is `base`.

See also cntrparam for the parameters that affect the drawing of contours, and clabel for control of labelling of the contours.

The surface can be switched off (see surface), giving a contour-only graph. Though it is possible to use size to enlarge the plot to fill the screen, more control over the output format can be obtained by writing the contour information to a file, and rereading it as a 2-d datafile plot:

 
      unset surface
      set contour
      set cntrparam ...
      set table 'filename'
      splot ...
      unset table
      # contour info now in filename
      set term <whatever>
      plot 'filename'

In order to draw contours, the data should be organized as "grid data". In such a file all the points for a single y-isoline are listed, then all the points for the next y-isoline, and so on. A single blank line (a line containing no characters other than blank spaces and a carriage return and/or a line feed) separates one y-isoline from the next. See also datafile.

See also contours demo (contours.dem) and contours with user defined levels demo (discrete.dem).


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2.21.13 data style

This form of the command is deprecated. Please see `set style data`.


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2.21.14 datafile

The datafile command options control interpretation of fields read from input data files by the `plot`, `splot`, and `fit` commands. Four such options are currently implemented.


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2.21.14.1 set datafile fortran

The `set datafile fortran` command enables a special check for values in the input file expressed as Fortran D or Q constants. This extra check slows down the input process, and should only be selected if you do in fact have datafiles containing Fortran D or Q constants. The option can be disabled again using `unset datafile fortran`.


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2.21.14.2 set datafile missing

The `set datafile missing` command allows you to tell `gnuplot` what character string is used in a data file to denote missing data. Exactly how this missing value will be treated depends on the using specifier of the `plot` or `splot` command.

Syntax:

 
      set datafile missing {"<string>"}
      show datafile missing
      unset datafile

Example:

 
      # Ignore entries containing IEEE NaN ("Not a Number") code
      set datafile missing "NaN"

Example:

 
      set datafile missing "?"
      set style data lines
      plot '-'
         1 10
         2 20
         3 ?
         4 40
         5 50
         e
      plot '-' using 1:2
         1 10
         2 20
         3 ?
         4 40
         5 50
         e
      plot '-' using 1:($2)
         1 10
         2 20
         3 ?
         4 40
         5 50
         e

The first `plot` will recognize only the first datum in the "3 ?" line. It will use the single-datum-on-a-line convention that the line number is "x" and the datum is "y", so the point will be plotted (in this case erroneously) at (2,3).

The second `plot` will correctly ignore the middle line. The plotted line will connect the points at (2,20) and (4,40).

The third `plot` will also correctly ignore the middle line, but the plotted line will not connect the points at (2,20) and (4,40).

There is no default character for `missing`, but in many cases any non-parsible string of characters found where a numerical value is expected will be treated as missing data.


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2.21.14.3 set datafile separator

The command `set datafile separator "<char>"` tells `gnuplot` that data fields in subsequent input files are separated by <char> rather than by whitespace. The most common use is to read in csv (comma-separated value) files written by spreadsheet or database programs. By default data fields are separated by whitespace.

Syntax:

 
      set datafile separator {"<char>" | whitespace}

Examples:

 
      # Input file contains tab-separated fields
      set datafile separator "\t"

 
      # Input file contains comma-separated values fields
      set datafile separator ","


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2.21.14.4 set datafile commentschars

The `set datafile commentschars` command allows you to tell `gnuplot` what characters are used in a data file to denote comments. Gnuplot will ignore rest of the line behind the specified characters if either of them is the first non-blank character on the line.

Syntax:

 
      set datafile commentschars {"<string>"}
      show datafile commentschars
      unset commentschars

Default value of the string is "#!" on VMS and "#" otherwise.

Then, the following line in a data file is completely ignored

 
    # 1 2 3 4

but the following

 
    1 # 3 4

produces rather unexpected plot unless

 
    set datafile missing '#'

is specified as well.

Example:

 
      set datafile commentschars "#!%"


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2.21.14.5 set datafile binary

The `set datafile binary` command is used to set the defaults when reading binary data files. The syntax matches precisely that used for commands `plot` and `splot`. See `binary` for details about <binary list>.

Syntax:

 
      set datafile binary <binary list>
      show datafile binary
      show datafile
      unset datafile

Examples:

 
      set datafile binary filetype=auto
      set datafile binary array=512x512 format="%uchar"


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2.21.15 decimalsign

The decimalsign command selects a decimal sign for numbers printed into tic labels or label strings.

Syntax:

 
      set decimalsign {<value> | locale {"<locale>"}}
      unset decimalsign
      show decimalsign

The argument <value> is a string to be used in place of the usual decimal point. Typical choices include the period, '.', and the comma, ',', but others may be useful, too. If you omit the <value> argument, the decimal separator is not modified from the usual default, which is a period. Unsetting decimalsign has the same effect as omitting <value>.

Example:

Correct typesetting in most European countries requires:

 
      set decimalsign ','

Please note: If you set an explicit string, this affects only numbers that are printed using gnuplot's gprintf() formatting routine, include axis tics. It does not affect the format expected for input data, and it does not affect numbers printed with the sprintf() formatting routine. To change the behavior of both input and output formatting, instead use the form

 
      set decimalsign locale

This instructs the program to use both input and output formats in accordance with the current setting of the LC_ALL, LC_NUMERIC, or LANG environmental variables.

 
      set decimalsign locale "foo"

This instructs the program to format all input and output in accordance with locale "foo", which must be installed. If locale "foo" is not found then an error message is printed and the decimal sign setting is unchanged. On linux systems you can get a list of the locales installed on your machine by typing "locale -a". A typical linux locale string is of the form "sl_SI.UTF-8". A typical Windows locale string is of the form "Slovenian_Slovenia.1250" or "slovenian". Please note that interpretation of the locale settings is done by the C library at runtime. Older C libraries may offer only partial support for locale settings such as the thousands grouping separator character.

 
      set decimalsign locale; set decimalsign "."

This sets all input and output to use whatever decimal sign is correct for the current locale, but over-rides this with an explicit '.' in numbers formatted using gnuplot's internal gprintf() function.


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2.21.16 dgrid3d

The dgrid3d command enables, and can set parameters for, non-grid to grid data mapping. See `splot grid_data` for more details about the grid data structure.

Syntax:

 
      set dgrid3d {<row_size>} {,{<col_size>} {,<norm>}}
      unset dgrid3d
      show dgrid3d

By default dgrid3d is disabled. When enabled, 3-d data read from a file are always treated as a scattered data set. A grid with dimensions derived from a bounding box of the scattered data and size as specified by the row/col_size parameters is created for plotting and contouring. The grid is equally spaced in x (rows) and in y (columns); the z values are computed as weighted averages of the scattered points' z values.

The third parameter, norm, controls the weighting: Each data point is weighted inversely by its distance from the grid point raised to the norm power. (Actually, the weights are given by the inverse of dx^norm + dy^norm, where dx and dy are the components of the separation of the grid point from each data point. For some norms that are powers of two, specifically 4, 8, and 16, the computation is optimized by using the Euclidean distance in the weight calculation, (dx^2+dy^2)^norm/2. However, any non-negative integer can be used.)

The closer the data point is to a grid point, the more effect it has on that grid point and the larger the value of norm the less effect more distant data points have on that grid point.

The dgrid3d option is a simple low pass filter that converts scattered data to a grid data set. More sophisticated approaches to this problem exist and should be used to preprocess the data outside `gnuplot` if this simple solution is found inadequate.

(The z values are found by weighting all data points, not by interpolating between nearby data points; also edge effects may produce unexpected and/or undesired results. In some cases, small norm values produce a grid point reflecting the average of distant data points rather than a local average, while large values of norm may produce "steps" with several grid points having the same value as the closest data point, rather than making a smooth transition between adjacent data points. Some areas of a grid may be filled by extrapolation, to an arbitrary boundary condition. The variables are not normalized; consequently the units used for x and y will affect the relative weights of points in the x and y directions.)

Examples:

 
      set dgrid3d 10,10,1     # defaults
      set dgrid3d ,,4

The first specifies that a grid of size 10 by 10 is to be constructed using a norm value of 1 in the weight computation. The second only modifies the norm, changing it to 4. See also scatter.dem: dgrid3d demo.


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2.21.17 dummy

The dummy command changes the default dummy variable names.

Syntax:

 
      set dummy {<dummy-var>} {,<dummy-var>}
      show dummy

By default, `gnuplot` assumes that the independent, or "dummy", variable for the `plot` command is "t" if in parametric or polar mode, or "x" otherwise. Similarly the independent variables for the `splot` command are "u" and "v" in parametric mode (`splot` cannot be used in polar mode), or "x" and "y" otherwise.

It may be more convenient to call a dummy variable by a more physically meaningful or conventional name. For example, when plotting time functions:

 
      set dummy t
      plot sin(t), cos(t)

At least one dummy variable must be set on the command; dummy by itself will generate an error message.

Examples:

 
      set dummy u,v
      set dummy ,s

The second example sets the second variable to s.


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2.21.18 encoding

The encoding command selects a character encoding. Syntax:

 
      set encoding {<value>}
      show encoding

Valid values are

 
   default     - tells a terminal to use its default encoding
   iso_8859_1  - the most common Western European font used by many
                 Unix workstations and by MS-Windows. This encoding is
                 known in the PostScript world as 'ISO-Latin1'.
   iso_8859_2  - used in Central and Eastern Europe
   iso_8859_15 - a variant of iso_8859_1 that includes the Euro symbol
   koi8r       - popular Unix cyrillic encoding
   koi8u       - ukrainian Unix cyrillic encoding
   cp437       - codepage for MS-DOS
   cp850       - codepage for OS/2, Western Europe
   cp852       - codepage for OS/2, Central and Eastern Europe
   cp1250      - codepage for MS Windows, Central and Eastern Europe

Generally you must set the encoding before setting the terminal type. Note that encoding is not supported by all terminal drivers and that the device must be able to produce the desired non-standard characters. The PostScript, X11 and wxt terminals support all encodings. OS/2 Presentation Manager switches automatically to codepage 912 for `iso_8859_2`.


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2.21.19 fit

The `fit` setting defines where the `fit` command writes its output. If this option was built into your version of gnuplot, it also controls whether parameter errors from the fit will be written into variables.

Syntax:

 
      set fit {logfile {"<filename>"}} {{no}errorvariables}
      unset fit
      show fit

The <filename> argument must be enclosed in single or double quotes.

If no filename is given or `unset fit` is used the log file is reset to its default value "fit.log" or the value of the environmental variable `FIT_LOG`.

Users of DOS-like platforms should note that the \ character has special significance in double-quoted strings, so single-quotes should be used for filenames in different directories, or you have to write \\ for each \. Or you can just use forward slashes, even though this is DOS.

If the given logfile name ends with a / or \, it is interpreted to be a directory name, and the actual filename will be "fit.log" in that directory.

If the `errorvariables` option is turned on, the error of each fitted parameter computed by `fit` will be copied to a user-defined variable whose name is formed by appending "_err" to the name of the parameter itself. This is useful mainly to put the parameter and its error onto a plot of the data and the fitted function, for reference, as in:

 
       set fit errorvariables
       fit f(x) 'datafile' using 1:2 via a, b
       print "error of a is:", a_err
       set label 'a=%6.2f', a, '+/- %6.2f', a_err
       plot 'datafile' using 1:2, f(x)


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2.21.20 fontpath

The fontpath setting defines additional locations for font files searched when including font files. Currently only the postscript terminal supports fontpath. If a file cannot be found in the current directory, the directories in fontpath are tried. Further documentation concerning the supported file formats is included in the postscript section of the documentation.

Syntax:

 
      set fontpath {"pathlist1" {"pathlist2"...}}
      show fontpath

Path names may be entered as single directory names, or as a list of path names separated by a platform-specific path separator, eg. colon (':') on Unix, semicolon (';') on DOS/Windows/OS/2/Amiga platforms. The fontpath, save and `save set` commands replace the platform-specific separator with a space character (' ') for maximum portability. If a directory name ends with an exclamation mark ('!') also the subdirectories of this directory are searched for font files.

If the environmental variable GNUPLOT_FONTPATH is set, its contents are appended to fontpath. If it is not set, a system dependent default value is used. It is set by testing several directories for existence when using the fontpath the first time. Thus, the first call of fontpath, fontpath, fontpath, `plot`, or `splot` with embedded font files takes a little more time. If you want to save this time you may set the environmental variable GNUPLOT_FONTPATH since probing is switched off, then. You can find out which is the default fontpath by using fontpath.

However, fontpath prints the contents of user defined fontpath and system fontpath separately. Also, the save and `save set` commands save only the user specified parts of fontpath, for portability reasons.

Many other terminal drivers access TrueType fonts via the gd library. For these drivers the font search path is controlled by the environmental variable GDFONTPATH.


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2.21.21 format

The format of the tic-mark labels can be set with the `set format` command.

Syntax:

 
      set format {<axes>} {"<format-string>"}
      set format {<axes>} {'<format-string>'}
      show format

where <axes> is either `x`, `y`, `xy`, `x2`, `y2`, `z`, `cb` or nothing (which refers to all axes at once). The length of the string representing a tic mark (after formatting with 'printf') is restricted to 100 characters. If the format string is omitted, the format will be returned to the default "% g". For LaTeX users, the format "$%g$" is often desirable. If the empty string "" is used, no label will be plotted with each tic, though the tic mark will still be plotted. To eliminate all tic marks, use xtics or ytics.

Newline (\n) is accepted in the format string. Use double-quotes rather than single-quotes to enable such interpretation. See also `syntax`.

The default format for both axes is "% g", but other formats such as "%.2f" or "%3.0em" are often desirable. Anything accepted by 'printf' when given a double precision number, and accepted by the terminal, will work. Some other options have been added. If the format string looks like a floating point format, then `gnuplot` tries to construct a reasonable format.

Characters not preceded by "%" are printed verbatim. Thus you can include spaces and labels in your format string, such as "%g m", which will put " m" after each number. If you want "%" itself, double it: "%g %%".

See also xtics for more information about tic labels, and decimalsign for how to use non-default decimal separators in numbers printed this way. See also electron demo (electron.dem).


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2.21.21.1 gprintf

The string function gprintf("format",x) uses gnuplot's own format specifiers, as do the gnuplot commands `set format`, timestamp, and others. These format specifiers are not the same as those used by the standard C-language routine sprintf(). Gnuplot also provides an sprintf("format",x,...) routine if you prefer. For a list of gnuplot's format options, see `format specifiers`.


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2.21.21.2 format specifiers

The acceptable formats (if not in time/date mode) are:

 
      Format       Explanation
      %f           floating point notation
      %e or %E     exponential notation; an "e" or "E" before the power
      %g or %G     the shorter of %e (or %E) and %f
      %x or %X     hex
      %o or %O     octal
      %t           mantissa to base 10
      %l           mantissa to base of current logscale
      %s           mantissa to base of current logscale; scientific power
      %T           power to base 10
      %L           power to base of current logscale
      %S           scientific power
      %c           character replacement for scientific power
      %P           multiple of pi

A 'scientific' power is one such that the exponent is a multiple of three. Character replacement of scientific powers (`"%c"`) has been implemented for powers in the range -18 to +18. For numbers outside of this range the format reverts to exponential.

Other acceptable modifiers (which come after the "%" but before the format specifier) are "-", which left-justifies the number; "+", which forces all numbers to be explicitly signed; " " (a space), which makes positive numbers have a space in front of them where negative numbers have "-"; "#", which places a decimal point after floats that have only zeroes following the decimal point; a positive integer, which defines the field width; "0" (the digit, not the letter) immediately preceding the field width, which indicates that leading zeroes are to be used instead of leading blanks; and a decimal point followed by a non-negative integer, which defines the precision (the minimum number of digits of an integer, or the number of digits following the decimal point of a float).

Some systems may not support all of these modifiers but may also support others; in case of doubt, check the appropriate documentation and then experiment.

Examples:

 
      set format y "%t"; set ytics (5,10)          # "5.0" and "1.0"
      set format y "%s"; set ytics (500,1000)      # "500" and "1.0"
      set format y "%+-12.3f"; set ytics(12345)    # "+12345.000  "
      set format y "%.2t*10^%+03T"; set ytic(12345)# "1.23*10^+04"
      set format y "%s*10^{%S}"; set ytic(12345)   # "12.345*10^{3}"
      set format y "%s %cg"; set ytic(12345)       # "12.345 kg"
      set format y "%.0P pi"; set ytic(6.283185)   # "2 pi"
      set format y "%.0f%%"; set ytic(50)          # "50%"

 
      set log y 2; set format y '%l'; set ytics (1,2,3)
      #displays "1.0", "1.0" and "1.5" (since 3 is 1.5 * 2^1)

There are some problem cases that arise when numbers like 9.999 are printed with a format that requires both rounding and a power.

If the data type for the axis is time/date, the format string must contain valid codes for the 'strftime' function (outside of `gnuplot`, type "man strftime"). See timefmt for a list of the allowed input format codes.


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2.21.21.3 time/date specifiers

In time/date mode, the acceptable formats are:

 
      Format       Explanation
      %a           abbreviated name of day of the week
      %A           full name of day of the week
      %b or %h     abbreviated name of the month
      %B           full name of the month
      %d           day of the month, 1--31
      %D           shorthand for "%m/%d/%y"
      %k           hour, 0--23 (one or two digits)
      %H           hour, 00--23 (always two digits)
      *l           hour, 1--12 (one or two digits)
      %I           hour, 01--12 (always two digits)
      %j           day of the year, 1--366
      %m           month, 1--12
      %M           minute, 0--60
      %p           "am" or "pm"
      %r           shorthand for "%I:%M:%S %p"
      %R           shorthand for "%H:%M"
      %S           second, 0--60
      %T           shorthand for "%H:%M:%S"
      %U           week of the year (week starts on Sunday)
      %w           day of the week, 0--6 (Sunday = 0)
      %W           week of the year (week starts on Monday)
      %y           year, 0-99
      %Y           year, 4-digit

Except for the non-numerical formats, these may be preceded by a "0" ("zero", not "oh") to pad the field length with leading zeroes, and a positive digit, to define the minimum field width (which will be overridden if the specified width is not large enough to contain the number). There is a 24-character limit to the length of the printed text; longer strings will be truncated.

Examples:

Suppose the text is "76/12/25 23:11:11". Then

 
      set format x                 # defaults to "12/25/76" \n "23:11"
      set format x "%A, %d %b %Y"  # "Saturday, 25 Dec 1976"
      set format x "%r %D"         # "11:11:11 pm 12/25/76"

Suppose the text is "98/07/06 05:04:03". Then

 
      set format x "%1y/%2m/%3d %01H:%02M:%03S"  # "98/ 7/  6 5:04:003"


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2.21.22 function style

This form of the command is deprecated. Please see `set style function`.


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2.21.23 functions

The `show functions` command lists all user-defined functions and their definitions.

Syntax:

 
      show functions

For information about the definition and usage of functions in `gnuplot`, please see `expressions`. See also splines as user defined functions (spline.dem) and use of functions and complex variables for airfoils (airfoil.dem).


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2.21.24 grid

The `set grid` command allows grid lines to be drawn on the plot.

Syntax:

 
      set grid {{no}{m}xtics} {{no}{m}ytics} {{no}{m}ztics}
               {{no}{m}x2tics} {{no}{m}y2tics}
               {{no}{m}cbtics}
               {polar {<angle>}}
               {layerdefault | front | back}
               { {linestyle <major_linestyle>}
                 | {linetype | lt <major_linetype>}
                   {linewidth | lw <major_linewidth>}
                 { , {linestyle | ls <minor_linestyle>}
                     | {linetype | lt <minor_linetype>}
                       {linewidth | lw <minor_linewidth>} } }
      unset grid
      show grid

The grid can be enabled and disabled for the major and/or minor tic marks on any axis, and the linetype and linewidth can be specified for major and minor grid lines, also via a predefined linestyle, as far as the active terminal driver supports this.

Additionally, a polar grid can be selected for 2-d plots--circles are drawn to intersect the selected tics, and radial lines are drawn at definable intervals. (The interval is given in degrees or radians, depending on the angles setting.) Note that a polar grid is no longer automatically generated in polar mode.

The pertinent tics must be enabled before `set grid` can draw them; `gnuplot` will quietly ignore instructions to draw grid lines at non-existent tics, but they will appear if the tics are subsequently enabled.

If no linetype is specified for the minor gridlines, the same linetype as the major gridlines is used. The default polar angle is 30 degrees.

If `front` is given, the grid is drawn on top of the graphed data. If `back` is given, the grid is drawn underneath the graphed data. Using `front` will prevent the grid from being obscured by dense data. The default setup, `layerdefault`, is equivalent to `back` for 2d plots. In 3D plots the default is to split up the grid and the graph box into two layers: one behind, the other in front of the plotted data and functions. Since hidden3d mode does its own sorting, it ignores all grid drawing order options and passes the grid lines through the hidden line removal machinery instead. These options actually affect not only the grid, but also the lines output by border and the various ticmarks (see xtics).

Z grid lines are drawn on the bottom of the plot. This looks better if a partial box is drawn around the plot--see border.


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2.21.25 hidden3d

The hidden3d command enables hidden line removal for surface plotting (see `splot`). Some optional features of the underlying algorithm can also be controlled using this command.

Syntax:

 
      set hidden3d {defaults} |
                   { {{offset <offset>} | {nooffset}}
                     {trianglepattern <bitpattern>}
                     {{undefined <level>} | {noundefined}}
                     {{no}altdiagonal}
                     {{no}bentover} }
      unset hidden3d
      show hidden3d

In contrast to the usual display in gnuplot, hidden line removal actually treats the given function or data grids as real surfaces that can't be seen through, so parts behind the surface will be hidden by it. For this to be possible, the surface needs to have 'grid structure' (see datafile about this), and it has to be drawn `with lines` or `with linespoints`.

When hidden3d is set, both the hidden portion of the surface and possibly its contours drawn on the base (see contour) as well as the grid will be hidden. Each surface has its hidden parts removed with respect to itself and to other surfaces, if more than one surface is plotted. Contours drawn on the surface (surface) don't work.

Labels and arrows are always visible and are unaffected. The key box is never hidden by the surface. As of gnuplot version 4.2, hidden3d also affects 3D plotting styles `with points`, `with labels`, and `with vectors`, even if no surface is present in the graph. Individual plots within the graph may be explicitly excluded from this processing by appending the extra option `nohidden3d` to the with specifier.

Hidden3d does not affect solid surfaces drawn using the pm3d mode. To achieve a similar effect for pm3d surfaces, use instead set `pm3d depthorder`.

Functions are evaluated at isoline intersections. The algorithm interpolates linearly between function points or data points when determining the visible line segments. This means that the appearance of a function may be different when plotted with hidden3d than when plotted with `nohidden3d` because in the latter case functions are evaluated at each sample. Please see samples and isosamples for discussion of the difference.

The algorithm used to remove the hidden parts of the surfaces has some additional features controllable by this command. Specifying `defaults` will set them all to their default settings, as detailed below. If `defaults` is not given, only explicitly specified options will be influenced: all others will keep their previous values, so you can turn on/off hidden line removal via `set {no}hidden3d`, without modifying the set of options you chose.

The first option, `offset`, influences the linestyle used for lines on the 'back' side. Normally, they are drawn in a linestyle one index number higher than the one used for the front, to make the two sides of the surface distinguishable. You can specify a different line style offset to add instead of the default 1, by `offset <offset>`. Option `nooffset` stands for `offset 0`, making the two sides of the surface use the same linestyle.

Next comes the option `trianglepattern <bitpattern>`. <bitpattern> must be a number between 0 and 7, interpreted as a bit pattern. Each bit determines the visibility of one edge of the triangles each surface is split up into. Bit 0 is for the 'horizontal' edges of the grid, Bit 1 for the 'vertical' ones, and Bit 2 for the diagonals that split each cell of the original grid into two triangles. The default pattern is 3, making all horizontal and vertical lines visible, but not the diagonals. You may want to choose 7 to see those diagonals as well.

The `undefined <level>` option lets you decide what the algorithm is to do with data points that are undefined (missing data, or undefined function values), or exceed the given x-, y- or z-ranges. Such points can either be plotted nevertheless, or taken out of the input data set. All surface elements touching a point that is taken out will be taken out as well, thus creating a hole in the surface. If <level> = 3, equivalent to option `noundefined`, no points will be thrown away at all. This may produce all kinds of problems elsewhere, so you should avoid this. <level> = 2 will throw away undefined points, but keep the out-of-range ones. <level> = 1, the default, will get rid of out-of-range points as well.

By specifying `noaltdiagonal`, you can override the default handling of a special case can occur if `undefined` is active (i.e. <level> is not 3). Each cell of the grid-structured input surface will be divided in two triangles along one of its diagonals. Normally, all these diagonals have the same orientation relative to the grid. If exactly one of the four cell corners is excluded by the `undefined` handler, and this is on the usual diagonal, both triangles will be excluded. However if the default setting of `altdiagonal` is active, the other diagonal will be chosen for this cell instead, minimizing the size of the hole in the surface.

The `bentover` option controls what happens to another special case, this time in conjunction with the `trianglepattern`. For rather crumply surfaces, it can happen that the two triangles a surface cell is divided into are seen from opposite sides (i.e. the original quadrangle is 'bent over'), as illustrated in the following ASCII art:

 
                                                              C----B
    original quadrangle:  A--B      displayed quadrangle:     |\   |
      ("set view 0,0")    | /|    ("set view 75,75" perhaps)  | \  |
                          |/ |                                |  \ |
                          C--D                                |   \|
                                                              A    D

If the diagonal edges of the surface cells aren't generally made visible by bit 2 of the <bitpattern> there, the edge CB above wouldn't be drawn at all, normally, making the resulting display hard to understand. Therefore, the default option of `bentover` will turn it visible in this case. If you don't want that, you may choose `nobentover` instead. See also hidden line removal demo (hidden.dem) and complex hidden line demo (singulr.dem).


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2.21.26 historysize

Note: the command historysize is only available when gnuplot has been configured with the GNU readline.

Syntax:

 
      set historysize <int>
      unset historysize

When leaving gnuplot, the value of historysize is used for truncating the history to at most that much lines. The default is 500. historysize will disable history truncation and thus allow an infinite number of lines to be written to the history file.


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2.21.27 isosamples

The isoline density (grid) for plotting functions as surfaces may be changed by the isosamples command.

Syntax:

 
      set isosamples <iso_1> {,<iso_2>}
      show isosamples

Each function surface plot will have <iso_1> iso-u lines and <iso_2> iso-v lines. If you only specify <iso_1>, <iso_2> will be set to the same value as <iso_1>. By default, sampling is set to 10 isolines per u or v axis. A higher sampling rate will produce more accurate plots, but will take longer. These parameters have no effect on data file plotting.

An isoline is a curve parameterized by one of the surface parameters while the other surface parameter is fixed. Isolines provide a simple means to display a surface. By fixing the u parameter of surface s(u,v), the iso-u lines of the form c(v) = s(u0,v) are produced, and by fixing the v parameter, the iso-v lines of the form c(u) = s(u,v0) are produced.

When a function surface plot is being done without the removal of hidden lines, samples controls the number of points sampled along each isoline; see samples and hidden3d. The contour algorithm assumes that a function sample occurs at each isoline intersection, so change in samples as well as isosamples may be desired when changing the resolution of a function surface/contour.


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2.21.28 key

The key command enables a key (or legend) describing plots on a plot.

The contents of the key, i.e., the names given to each plotted data set and function and samples of the lines and/or symbols used to represent them, are determined by the `title` and with options of the {`s`}`plot` command. Please see `plot title` and with for more information.

Syntax:

 
      set key {on|off} {default}
              {{inside | outside} | {lmargin | rmargin | tmargin | bmargin}
                | {at <position>}}
              {left | right | center} {top | bottom | center}
              {vertical | horizontal} {Left | Right}
              {{no}reverse} {{no}invert}
              {samplen <sample_length>} {spacing <vertical_spacing>}
              {width <width_increment>}
              {height <height_increment>}
              {{no}autotitle {columnheader}}
              {title "<text>"} {{no}enhanced}
              {{no}box { {linestyle | ls <line_style>}
                         | {linetype | lt <line_type>}
                           {linewidth | lw <line_width>}}}
      unset key
      show key

Plots may be drawn with no visible key by requesting `set key off` or key.

Elements within the key are stacked according to `vertical` or `horizontal`. In the case of `vertical`, the key occupies as few columns as possible. That is, elements are aligned in a column until running out of vertical space at which point a new column is started. In the case of `horizontal`, the key occupies as few rows as possible.

By default the key is placed in the upper right inside corner of the graph. The keywords `left`, `right`, `top`, `bottom`, `center`, `inside`, `outside`, lmargin, rmargin, tmargin, bmargin (, `above`, `over`, `below` and `under`) may be used to automatically place the key in other positions of the graph. Also an `at <position>` may be given to indicate precisely where the plot should be placed. In this case, the keywords `left`, `right`, `top`, `bottom` and `center` serve an analogous purpose for alignment.

To understand positioning, the best concept is to think of a region, i.e., inside/outside, or one of the margins. Along with the region, keywords `left/center/right` (l/c/r) and `top/center/bottom` (t/c/b) control where within the particular region the key should be placed.

When in `inside` mode, the keywords `left` (l), `right` (r), `top` (t), `bottom` (b), and `center` (c) push the key out toward the plot boundary as illustrated:

 
     t/l   t/c   t/r

 
     c/l    c    c/r

 
     b/l   b/c   b/r

When in `outside` mode, automatic placement is similar to the above illustration, but with respect to the view, rather than the graph boundary. That is, a border is moved inward to make room for the key outside of the plotting area, although this may interfere with other labels and may cause an error on some devices. The particular plot border that is moved depends upon the position described above and the stacking direction. For options centered in one of the dimensions, there is no ambiguity about which border to move. For the corners, when the stack direction is `vertical`, the left or right border is moved inward appropriately. When the stack direction is `horizontal`, the top or bottom border is moved inward appropriately.

The margin syntax allows automatic placement of key regardless of stack direction. When one of the margins lmargin (lm), rmargin (rm), tmargin (tm), and bmargin (bm) is combined with a single, non-conflicting direction keyword, the following illustrated positions may contain the key:

 
          l/tm  c/tm  r/tm

 
     t/lm                  t/rm

 
     c/lm                  c/rm

 
     b/lm                  b/rm

 
          l/bm  c/bm  r/bm

Keywords `above` and `over` are synonymous with tmargin. For version compatibility, `above` or `over` without an additional l/c/r or stack direction keyword uses `center` and `horizontal`. Keywords `below` and `under` are synonymous with bmargin. For compatibility, `below` or `under` without an additional l/c/r or stack direction keyword uses `center` and `horizontal`. A further compatibility issue is that `outside` appearing without an additional t/b/c or stack direction keyword uses `top`, `right` and `vertical` (i.e., the same as t/rm above).

The <position> can be a simple x,y,z as in previous versions, but these can be preceded by one of five keywords (`first`, `second`, `graph`, `screen`, `character`) which selects the coordinate system in which the position of the first sample line is specified. See `coordinates` for more details. The effect of `left`, `right`, `top`, `bottom`, and `center` when <position> is given is to align the key as though it were text positioned using the label command, i.e., `left` means left align with key to the right of <position>, etc.

Justification of the labels within the key is controlled by `Left` or `Right` (default is `Right`). The text and sample can be reversed (`reverse`) and a box can be drawn around the key (`box {...}`) in a specified `linetype` and `linewidth`, or a user-defined `linestyle`. Note that not all terminal drivers support linewidth selection, though.

By default the first plot label is at the top of the key and successive labels are entered below it. The `invert` option causes the first label to be placed at the bottom of the key, with successive labels entered above it. This option is useful to force the vertical ordering of labels in the key to match the order of box types in a stacked histogram.

The length of the sample line can be controlled by `samplen`. The sample length is computed as the sum of the tic length and <sample_length> times the character width. `samplen` also affects the positions of point samples in the key since these are drawn at the midpoint of the sample line, even if the sample line itself is not drawn.

The vertical spacing between lines is controlled by `spacing`. The spacing is set equal to the product of the pointsize, the vertical tic size, and <vertical_spacing>. The program will guarantee that the vertical spacing is no smaller than the character height.

The <width_increment> is a number of character widths to be added to or subtracted from the length of the string. This is useful only when you are putting a box around the key and you are using control characters in the text. `gnuplot` simply counts the number of characters in the string when computing the box width; this allows you to correct it.

The <height_increment> is a number of character heights to be added to or subtracted from the height of the key box. This is useful mainly when you are putting a box around the key, otherwise it can be used to adjust the vertical shift of automatically chosen key position by <height_increment>/2.

All plotted curves of `plot`s and `splot`s are titled according to the default option `autotitles`. The automatic generation of titles can be suppressed by `noautotitles`; then only those titles explicitly defined by `(s)plot ... title ...` will be drawn.

The `set key autotitle columnheader` option is available if gnuplot was built with -enable-datastrings. This command causes the first entry in each column of plotted data to be interpreted as a text string and used as a title for the corresponding plot. If the quantity being plotted is a function of data from several columns, gnuplot may be confused as to which column to draw the title from. In this case it is necessary to specify the column explicitly in the plot command, e.g. `plot "datafile" using (($2+$3)/$4) title 3 with lines`.

A title can be put on the key (`title "<text>"`)--see also `syntax` for the distinction between text in single- or double-quotes. The key title uses the same justification as do the plot titles.

An explicitly given title is typeset using enhanced text properties on terminals supporting this, see `enhanced text` for more details. This default behavior can be switched off by the `noenhanced` option.

The defaults for key are `on`, `right`, `top`, `vertical`, `Right`, `noreverse`, `noinvert`, `samplen 4`, `spacing 1.25`, `title ""`, and `nobox`. The default <linetype> is the same as that used for the plot borders. Entering `set key default` returns the key to its default configuration.

The key is drawn as a sequence of lines, with one plot described on each line. On the right-hand side (or the left-hand side, if `reverse` is selected) of each line is a representation that attempts to mimic the way the curve is plotted. On the other side of each line is the text description (the line title), obtained from the `plot` command. The lines are vertically arranged so that an imaginary straight line divides the left- and right-hand sides of the key. It is the coordinates of the top of this line that are specified with the key command. In a `plot`, only the x and y coordinates are used to specify the line position. For a `splot`, x, y and z are all used as a 3-d location mapped using the same mapping as the graph itself to form the required 2-d screen position of the imaginary line.

When using the TeX or PostScript drivers, or similar drivers where formatting information is embedded in the string, `gnuplot` is unable to calculate correctly the width of the string for key positioning. If the key is to be positioned at the left, it may be convenient to use the combination `set key left Left reverse`. The box and gap in the grid will be the width of the literal string.

If `splot` is being used to draw contours, the contour labels will be listed in the key. If the alignment of these labels is poor or a different number of decimal places is desired, the label format can be specified. See clabel for details.

Examples:

This places the key at the default location:

 
      set key default

This disables the key:

 
      unset key

This places a key at coordinates 2,3.5,2 in the default (first) coordinate system:

 
      set key at 2,3.5,2

This places the key below the graph:

 
      set key below

This places the key in the bottom left corner, left-justifies the text, gives it a title, and draws a box around it in linetype 3:

 
      set key left bottom Left title 'Legend' box 3


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2.21.29 label

Arbitrary labels can be placed on the plot using the label command.

Syntax:

 
      set label {<tag>} {"<label text>"} {at <position>}
                {left | center | right}
                {norotate | rotate {by <degrees>}}
                {font "<name>{,<size>}"}
                {noenhanced}
                {front | back}
                {textcolor <colorspec>}
                {point <pointstyle> | nopoint}
                {offset <offset>}
      unset label {<tag>}
      show label

The <position> is specified by either x,y or x,y,z, and may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. See `coordinates` for details.

The tag is an integer that is used to identify the label. If no <tag> is given, the lowest unused tag value is assigned automatically. The tag can be used to delete or modify a specific label. To change any attribute of an existing label, use the label command with the appropriate tag, and specify the parts of the label to be changed.

The <label text> can be a string constant, a string variable, or a string- valued expression. See `strings`, sprintf, and `gprintf`.

By default, the text is placed flush left against the point x,y,z. To adjust the way the label is positioned with respect to the point x,y,z, add the justification parameter, which may be `left`, `right` or `center`, indicating that the point is to be at the left, right or center of the text. Labels outside the plotted boundaries are permitted but may interfere with axis labels or other text.

If `rotate` is given, the label is written vertically (if the terminal can do so, of course). If `rotate by <degrees>` is given, conforming terminals will try to write the text at the specified angle; non-conforming terminals will treat this as vertical text.

Font and its size can be chosen explicitly by `font "<name>{,<size>}"` if the terminal supports font settings. Otherwise the default font of the terminal will be used.

Normally the enhanced text mode string interpretation, if enabled for the current terminal, is applied to all text strings including label text. The `noenhanced` property can be used to exempt a specific label from the enhanced text mode processing. The can be useful if the label contains underscores, for example. See `enhanced text`.

If `front` is given, the label is written on top of the graphed data. If `back` is given (the default), the label is written underneath the graphed data. Using `front` will prevent a label from being obscured by dense data.

`textcolor <colorspec>` changes the color of the label text. <colorspec> can be a linetype, an rgb color, or a palette mapping. See help for colorspec and palette. `textcolor` may be abbreviated `tc`.

 
   `tc default` resets the text color to its default state.
   `tc lt <n>` sets the text color to that of line type <n>.
   `tc ls <n>` sets the text color to that of line style <n>.
   `tc palette z` selects a palette color corresponding to the label z position.
   `tc palette cb <val>` selects a color corresponding to <val> on the colorbar.
   `tc palette fraction <val>`, with 0<=val<=1, selects a color corresponding to
       the mapping [0:1] to grays/colors of the palette.
   `tc rgb "#RRGGBB"` selects an arbitrary 24-bit RGB color.

If a <pointstyle> is given, using keywords `lt`, `pt` and `ps`, see style, a point with the given style and color of the given line type is plotted at the label position and the text of the label is displaced slightly. This option is used by default for placing labels in `mouse` enhanced terminals. Use `nopoint` to turn off the drawing of a point near the label (this is the default).

The displacement defaults to 1,1 in pointsize units if a <pointstyle> is given, 0,0 if no <pointstyle> is given. The displacement can be controlled by the optional `offset <offset>` where <offset> is specified by either x,y or x,y,z, and may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. See `coordinates` for details.

If one (or more) axis is timeseries, the appropriate coordinate should be given as a quoted time string according to the timefmt format string. See xdata and timefmt.

The EEPIC, Imagen, LaTeX, and TPIC drivers allow \\ in a string to specify a newline.

Examples:

To set a label at (1,2) to "y=x", use:

 
      set label "y=x" at 1,2

To set a Sigma of size 24, from the Symbol font set, at the center of the graph, use:

 
      set label "S" at graph 0.5,0.5 center font "Symbol,24"

To set a label "y=x^2" with the right of the text at (2,3,4), and tag the label as number 3, use:

 
      set label 3 "y=x^2" at 2,3,4 right

To change the preceding label to center justification, use:

 
      set label 3 center

To delete label number 2, use:

 
      unset label 2

To delete all labels, use:

 
      unset label

To show all labels (in tag order), use:

 
      show label

To set a label on a graph with a timeseries on the x axis, use, for example:

 
      set timefmt "%d/%m/%y,%H:%M"
      set label "Harvest" at "25/8/93",1

To display a freshly fitted parameter on the plot with the data and the fitted function, do this after the `fit`, but before the `plot`:

 
      set label sprintf("a = %3.5g",par_a) at 30,15
      bfit = gprintf("b = %s*10^%S",par_b)
      set label bfit at 30,20

To set a label displaced a little bit from a small point:

 
      set label 'origin' at 0,0 point lt 1 pt 2 ps 3 offset 1,-1

To set a label whose color matches the z value (in this case 5.5) of some point on a 3D splot colored using pm3d:

 
      set label 'text' at 0,0,5.5 tc palette z


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2.21.30 lmargin

The command lmargin sets the size of the left margin. Please see margin for details.


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2.21.31 loadpath

The loadpath setting defines additional locations for data and command files searched by the call, `load`, `plot` and `splot` commands. If a file cannot be found in the current directory, the directories in loadpath are tried.

Syntax:

 
      set loadpath {"pathlist1" {"pathlist2"...}}
      show loadpath

Path names may be entered as single directory names, or as a list of path names separated by a platform-specific path separator, eg. colon (':') on Unix, semicolon (';') on DOS/Windows/OS/2/Amiga platforms. The loadpath, save and `save set` commands replace the platform-specific separator with a space character (' ') for maximum portability.

If the environment variable GNUPLOT_LIB is set, its contents are appended to loadpath. However, loadpath prints the contents of user defined loadpath and system loadpath separately. Also, the save and `save set` commands save only the user specified parts of loadpath, for portability reasons.


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2.21.32 locale

The locale setting determines the language with which `{x,y,z}{d,m}tics` will write the days and months.

Syntax:

 
      set locale {"<locale>"}

<locale> may be any language designation acceptable to your installation. See your system documentation for the available options. The default value is determined from the LC_TIME, LC_ALL, or LANG environment variables.

To change the decimal point locale, see decimalsign.


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2.21.33 logscale

Syntax:

 
      set logscale <axes> <base>
      unset logscale <axes>
      show logscale

where <axes> may be any combination of `x`, `x2`, `y`, `y2`, `z`, and `cb` in any order, and where <base> is the base of the log scaling. If <base> is not given, then 10 is assumed. If <axes> is not given, then all axes are assumed. logscale turns off log scaling for the specified axes.

Examples:

To enable log scaling in both x and z axes:

 
      set logscale xz

To enable scaling log base 2 of the y axis:

 
      set logscale y 2

To enable z and color log axes for a pm3d plot:

 
      set logscale zcb

To disable z axis log scaling:

 
      unset logscale z


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2.21.34 macros

If command line macro substitution is enabled, then tokens in the command line of the form @<stringvariablename> will be replaced by the text string contained in <stringvariablename>. See `substitution`.

Syntax:

 
     set macros


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2.21.35 mapping

If data are provided to `splot` in spherical or cylindrical coordinates, the mapping command should be used to instruct `gnuplot` how to interpret them.

Syntax:

 
      set mapping {cartesian | spherical | cylindrical}

A cartesian coordinate system is used by default.

For a spherical coordinate system, the data occupy two or three columns (or using entries). The first two are interpreted as the azimuthal and polar angles theta and phi (or "longitude" and "latitude"), in the units specified by angles. The radius r is taken from the third column if there is one, or is set to unity if there is no third column. The mapping is:

 
      x = r * cos(theta) * cos(phi)
      y = r * sin(theta) * cos(phi)
      z = r * sin(phi)

Note that this is a "geographic" spherical system, rather than a "polar" one (that is, phi is measured from the equator, rather than the pole).

For a cylindrical coordinate system, the data again occupy two or three columns. The first two are interpreted as theta (in the units specified by angles) and z. The radius is either taken from the third column or set to unity, as in the spherical case. The mapping is:

 
      x = r * cos(theta)
      y = r * sin(theta)
      z = z

The effects of mapping can be duplicated with the using filter on the `splot` command, but mapping may be more convenient if many data files are to be processed. However even if mapping is used, using may still be necessary if the data in the file are not in the required order.

mapping has no effect on `plot`. world.dem: mapping demos.


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2.21.36 margin

The computed margins can be overridden by the margin commands. margin shows the current settings.

Syntax:

 
      set bmargin {<margin>}
      set lmargin {<margin>}
      set rmargin {<margin>}
      set tmargin {<margin>}
      show margin

The units of <margin> are character heights or widths, as appropriate. A positive value defines the absolute size of the margin. A negative value (or none) causes `gnuplot` to revert to the computed value. For 3D plots, only the left margin setting has any effect so far.

Normally the margins of a plot are automatically calculated based on tics, tic labels, axis labels, the plot title, the timestamp and the size of the key if it is outside the borders. If, however, tics are attached to the axes (`set xtics axis`, for example), neither the tics themselves nor their labels will be included in either the margin calculation or the calculation of the positions of other text to be written in the margin. This can lead to tic labels overwriting other text if the axis is very close to the border.


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2.21.37 mouse

The command `set mouse` enables mouse actions. Currently the pm, x11, ggi, windows and wxt terminals are mouse enhanced. There are two mouse modes. The 2d-graph mode works for 2d graphs and for maps (i.e. splots with view having z-rotation 0, 90, 180, 270 or 360 degrees, including `set view map`) and it allows tracing the position over graph, zooming, annotating graph etc. For 3d graphs `splot`, the view and scaling of the graph can be changed with mouse buttons 1 and 2. If additionally to these buttons the modifier <ctrl> is hold down, the coordinate system only is rotated which is useful for large data sets. A vertical motion of Button 2 with the shift key hold down changes the ticslevel.

Mousing is not available in multiplot mode. When multiplot is finished using multiplot, then the mouse will be turned on again and acts on the last plot (like replot does).

Syntax:

 
      set mouse {doubleclick <ms>} {nodoubleclick} \
                {{no}zoomcoordinates} \
                {noruler | ruler {at x,y}} \
                {polardistance{deg|tan} | nopolardistance} \
                {format <string>} \
                {clipboardformat <int>/<string>} \
                {mouseformat <int>/<string>} \
                {{no}labels} {labeloptions <string>} \
                {{no}zoomjump} {{no}verbose}
      unset mouse

The doubleclick resolution is given in milliseconds and used for Button 1 which copies the current mouse position to the `clipboard`. If you want that to be done by single clicking a value of 0 ms can be used. The default value is 300 ms.

The option `zoomcoordinates` determines if the coordinates of the zoom box are drawn at the edges while zooming. This is on by default.

The options `noruler` and `ruler` switch the ruler off and on, the latter optionally at given `coordinates`. This corresponds to the default key binding 'r'.

The option `polardistance` determines if the distance between the mouse cursor and the ruler is also shown in polar coordinates (distance and angle in degrees or tangent (slope)). This corresponds to the default key binding '5'.

The `format` option takes a fprintf like format string which determines how floating point numbers are printed to the drivers window and the clipboard. The default is "% #g".

`clipboardformat` and `mouseformat` are used for formatting the text on Button1 and Button2 actions - copying the coordinates to the clipboard and temporarily annotating the mouse position. This corresponds to the key bindings '1', '2', '3', '4' (see the drivers's help window). If the argument is a string this string is used as c format specifier and should contain two float specifiers, e.g. `set mouse mouseformat "mouse = %5.2g, %10.2f"`. Use `set mouse mouseformat ""` to turn this string off again.

The following formats are available (format 6 may only be selected if the format string was specified already):

 
 0   real coordinates in  brackets e.g. [1.23, 2.45]
 1   real coordinates w/o brackets e.g.  1.23, 2.45
 2   x == timefmt                       [(as set by timefmt), 2.45]
 3   x == date                          [31. 12. 1999, 2.45]
 4   x == time                          [23:59, 2.45]
 5   x == date / time                   [31. 12. 1999 23:59, 2.45]
 6   alt. format, specified as string   ""

Choose the option `labels` to get real gnuplot labels on Button 2. (The default is `nolabels` which makes Button 2 drawing only temporary annotations at the mouse positions). The labels are drawn with the current setting of `mouseformat`. `labeloptions` controls which options are passed to the label command. The default is "pointstyle 1" which will plot a small plus at the label position. Note that the pointsize is taken from the pointsize command. Labels can be removed by holding the Ctrl-Key down while clicking with Button 2 on the label's point. The threshold for how close you must be to the label is also determined by the pointsize.

If the option `zoomjump` is on, the mouse pointer will be automatically offset a small distance after starting a zoom region with button 3. This can be useful to avoid a tiny (or even empty) zoom region. `zoomjump` is off by default.

If the option `verbose` is turned on the communication commands are shown during execution. This option can also be toggled by hitting `6` in the driver's window. `verbose` is off by default.

Press 'h' in the driver's window for a short summary of the mouse and key bindings. This will also display user defined bindings or `hotkeys` which can be defined using the bind command, see help for bind. Note, that user defined `hotkeys` may override the default bindings.

Press 'q' in the driver's window to close the window. This key cannot be overridden with the bind command.

See also help for bind and label.


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2.21.37.1 X11 mouse

If multiple X11 plot windows have been opened using the `set term x11 <n>` terminal option, then only the current plot window supports the entire range of mouse commands and hotkeys. The other windows will, however, continue to display mouse coordinates at the lower left.

For consistency with other screen terminals, X11 mouse support is turned on by default, wherever the standard input comes from. However, on some UNIX flavors, special input devices as /dev/null might not be `select-able`; using such devices with the mouse turned on will hang gnuplot. Please turn off mousing with `unset mouse` if you are in this situation.


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2.21.38 multiplot

The command multiplot places `gnuplot` in the multiplot mode, in which several plots are placed on the same page, window, or screen.

Syntax:

 
      set multiplot { layout <rows>,<cols>
                      {rowsfirst|columnsfirst} {downwards|upwards}
                      {title <page title>}
                      {scale <xscale>{,<yscale>}} {offset <xoff>{,<yoff>}}
                    }
      unset multiplot

For some terminals, no plot is displayed until the command multiplot is given, which causes the entire page to be drawn and then returns gnuplot to its normal single-plot mode. For other terminals, each separate `plot` command produces an updated display, either by redrawing all previous ones and the newly added plot, or by just adding the new plot to the existing display.

The area to be used by the next plot is not erased before doing the new plot. The clear command can be used to do this if wanted, as is typically the case for "inset" plots.

Any labels or arrows that have been defined will be drawn for each plot according to the current size and origin (unless their coordinates are defined in the `screen` system). Just about everything else that can be `set` is applied to each plot, too. If you want something to appear only once on the page, for instance a single time stamp, you'll need to put a `set time`/`unset time` pair around one of the `plot`, `splot` or replot commands within the multiplot/multiplot block.

The multiplot title is separate from the individual plot titles, if any. Space is reserved for it at the top of the page, spanning the full width of the canvas.

The commands origin and size must be used to correctly position each plot if no layout is specified or if fine tuning is desired. See origin and size for details of their usage.

Example:

 
      set multiplot
      set size 0.4,0.4
      set origin 0.1,0.1
      plot sin(x)
      set size 0.2,0.2
      set origin 0.5,0.5
      plot cos(x)
      unset multiplot

This displays a plot of cos(x) stacked above a plot of sin(x).

size and origin refer to the entire plotting area used for each plot. Please also see size. If you want to have the axes themselves line up, you can guarantee that the margins are the same size with the margin commands. See margin for their use. Note that the margin settings are absolute, in character units, so the appearance of the graph in the remaining space will depend on the screen size of the display device, e.g., perhaps quite different on a video display and a printer.

With the `layout` option you can generate simple multiplots without having to give the size and origin commands before each plot: Those are generated automatically, but can be overridden at any time. With `layout` the display will be divided by a grid with <rows> rows and <cols> columns. This grid is filled rows first or columns first depending on whether the corresponding option is given in the multiplot command. The stack of plots can grow `downwards` or `upwards`. Default is `rowsfirst` and `downwards`.

Each plot can be scaled by `scale` and shifted with `offset`; if the y-values for scale or offset are omitted, the x-value will be used. multiplot will turn off the automatic layout and restore the values of size and origin as they were before `set multiplot layout`.

Example:

 
      set size 1,1
      set origin 0,0
      set multiplot layout 3,2 columnsfirst scale 1.1,0.9
      [ up to 6 plot commands here ]
      unset multiplot

The above example will produce 6 plots in 2 columns filled top to bottom, left to right. Each plot will have a horizontal size of 1.1/2 and a vertical size of 0.9/3.

See also multiplot demo (multiplt.dem)


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2.21.39 mx2tics

Minor tic marks along the x2 (top) axis are controlled by mx2tics. Please see mxtics.


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2.21.40 mxtics

Minor tic marks along the x axis are controlled by mxtics. They can be turned off with mxtics. Similar commands control minor tics along the other axes.

Syntax:

 
      set mxtics {<freq> | default}
      unset mxtics
      show mxtics

The same syntax applies to mytics, mztics, mx2tics, my2tics and `mcbtics`.

<freq> is the number of sub-intervals (NOT the number of minor tics) between major tics (the default for a linear axis is either two or five depending on the major tics, so there are one or four minor tics between major tics). Selecting `default` will return the number of minor ticks to its default value.

If the axis is logarithmic, the number of sub-intervals will be set to a reasonable number by default (based upon the length of a decade). This will be overridden if <freq> is given. However the usual minor tics (2, 3, ..., 8, 9 between 1 and 10, for example) are obtained by setting <freq> to 10, even though there are but nine sub-intervals.

To set minor tics at arbitrary positions, use the ("<label>" <pos> <level>, ...) form of `set {x|x2|y|y2|z}tics` with <label> empty and <level> set to 1.

The `set m{x|x2|y|y2|z}tics` commands work only when there are uniformly spaced major tics. If all major tics were placed explicitly by `set {x|x2|y|y2|z}tics`, then minor tic commands are ignored. Implicit major tics and explicit minor tics can be combined using `set {x|x2|y|y2|z}tics` and `set {x|x2|y|y2|z}tics add`.

Examples:

 
      set xtics 0, 5, 10
      set xtics add (7.5)
      set mxtics 5

Major tics at 0,5,7.5,10, minor tics at 1,2,3,4,6,7,8,9

 
      set logscale y
      set format y ""
      set ytics 1e-6, 10, 1
      set ytics add ("1" 1, ".1" 0.1, ".01" 0.01, "10^-3" 0.001, \
                     "10^-4" 0.0001)
      set mytics 10

Major tics with special formatting, minor tics at log positions

By default, minor tics are off for linear axes and on for logarithmic axes. They inherit the settings for `axis|border` and `{no}mirror` specified for the major tics. Please see xtics for information about these.


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2.21.41 my2tics

Minor tic marks along the y2 (right-hand) axis are controlled by my2tics. Please see mxtics.


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2.21.42 mytics

Minor tic marks along the y axis are controlled by mytics. Please see mxtics.


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2.21.43 mztics

Minor tic marks along the z axis are controlled by mztics. Please see mxtics.


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2.21.44 offsets

Offsets provide a mechanism to put a boundary around the data inside of an autoscaled graph.

Syntax:

 
      set offsets <left>, <right>, <top>, <bottom>
      unset offsets
      show offsets

Each offset may be a constant or an expression. Each defaults to 0. Left and right offsets are given in units of the x axis, top and bottom offsets in units of the y axis. A positive offset expands the graph in the specified direction, e.g., a positive bottom offset makes ymin more negative. Negative offsets, while permitted, can have unexpected interactions with autoscaling and clipping.

Offsets are ignored in `splot`s.

Example:

 
      set offsets 0, 0, 2, 2
      plot sin(x)

This graph of sin(x) will have a y range [-3:3] because the function will be autoscaled to [-1:1] and the vertical offsets are each two.


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2.21.45 origin

The origin command is used to specify the origin of a plotting surface (i.e., the graph and its margins) on the screen. The coordinates are given in the `screen` coordinate system (see `coordinates` for information about this system).

Syntax:

 
      set origin <x-origin>,<y-origin>


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2.21.46 output

By default, screens are displayed to the standard output. The output command redirects the display to the specified file or device.

Syntax:

 
      set output {"<filename>"}
      show output

The filename must be enclosed in quotes. If the filename is omitted, any output file opened by a previous invocation of output will be closed and new output will be sent to STDOUT. (If you give the command `set output "STDOUT"`, your output may be sent to a file named "STDOUT"! ["May be", not "will be", because some terminals, like `x11` or `wxt`, ignore output.])

MSDOS users should note that the \ character has special significance in double-quoted strings, so single-quotes should be used for filenames in different directories.

When both `set terminal` and output are used together, it is safest to give `set terminal` first, because some terminals set a flag which is needed in some operating systems. This would be the case, for example, if the operating system needs to know whether or not a file is to be formatted in order to open it properly.

On machines with popen functions (Unix), output can be piped through a shell command if the first non-whitespace character of the filename is '|'. For instance,

 
      set output "|lpr -Plaser filename"
      set output "|lp -dlaser filename"

On MSDOS machines, `set output "PRN"` will direct the output to the default printer. On VMS, output can be sent directly to any spooled device. It is also possible to send the output to DECnet transparent tasks, which allows some flexibility.


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2.21.47 parametric

The `set parametric` command changes the meaning of `plot` (`splot`) from normal functions to parametric functions. The command `unset parametric` restores the plotting style to normal, single-valued expression plotting.

Syntax:

 
      set parametric
      unset parametric
      show parametric

For 2-d plotting, a parametric function is determined by a pair of parametric functions operating on a parameter. An example of a 2-d parametric function would be `plot sin(t),cos(t)`, which draws a circle (if the aspect ratio is set correctly--see size). `gnuplot` will display an error message if both functions are not provided for a parametric `plot`.

For 3-d plotting, the surface is described as x=f(u,v), y=g(u,v), z=h(u,v). Therefore a triplet of functions is required. An example of a 3-d parametric function would be `cos(u)*cos(v),cos(u)*sin(v),sin(u)`, which draws a sphere. `gnuplot` will display an error message if all three functions are not provided for a parametric `splot`.

The total set of possible plots is a superset of the simple f(x) style plots, since the two functions can describe the x and y values to be computed separately. In fact, plots of the type t,f(t) are equivalent to those produced with f(x) because the x values are computed using the identity function. Similarly, 3-d plots of the type u,v,f(u,v) are equivalent to f(x,y).

Note that the order the parametric functions are specified is xfunction, yfunction (and zfunction) and that each operates over the common parametric domain.

Also, the `set parametric` function implies a new range of values. Whereas the normal f(x) and f(x,y) style plotting assume an xrange and yrange (and zrange), the parametric mode additionally specifies a trange, urange, and vrange. These ranges may be set directly with trange, urange, and vrange, or by specifying the range on the `plot` or `splot` commands. Currently the default range for these parametric variables is [-5:5]. Setting the ranges to something more meaningful is expected.


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2.21.48 plot

The `show plot` command shows the current plotting command as it results from the last `plot` and/or `splot` and possible subsequent replot commands.

In addition, the `show plot add2history` command adds this current plot command into the `history`. It is useful if you have used replot to add more curves to the current plot and you want to edit the whole command now.


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2.21.49 pm3d

pm3d is an `splot` style for drawing palette-mapped 3d and 4d data as color/gray maps and surfaces. It uses a pm3d algorithm which allows plotting gridded as well as non-gridded data without preprocessing, even when the data scans do not have the same number of points.

Drawing of color surfaces is available on terminals supporting filled colored polygons with color mapping specified by palette. Currently supported terminals include

 
  Screen terminals:
    OS/2 Presentation Manager
    X11
    Linux VGA (vgagl)
    GGI
    Windows
    AquaTerm (Mac OS X)
    wxWidgets (wxt)
  Files:
    PostScript
    pslatex, pstex, epslatex
    gif, png, jpeg
    (x)fig
    tgif
    cgm
    pdf
    svg
    emf

Let us first describe how a map/surface is drawn. The input data come from an evaluated function or from an file. Each surface consists of a sequence of separate scans (isolines). The pm3d algorithm fills the region between two neighbouring points in one scan with another two points in the next scan by a gray (or color) according to z-values (or according to an additional 'color' column, see help for using) of these 4 corners; by default the 4 corner values are averaged, but this can be changed by the option `corners2color`. In order to get a reasonable surface, the neighbouring scans should not cross and the number of points in the neighbouring scans should not differ too much; of course, the best plot is with scans having same number of points. There are no other requirements (e.g. the data need not be gridded). Another advantage is that the pm3d algorithm does not draw anything outside of the input (measured or calculated) region.

Surface coloring works with the following input data:

1. splot of function or of data file with one or three data columns: The gray/color scale is obtained by mapping the averaged (or `corners2color`) z-coordinate of the four corners of the above-specified quadrangle into the range [min_color_z,max_color_z] of zrange or cbrange providing a gray value in the range [0:1]. This value can be used directly as the gray for gray maps. The normalized gray value can be further mapped into a color--see palette for the complete description.

2. splot of data file with two or four data columns: The gray/color value is obtained by using the last-column coordinate instead of the z-value, thus allowing the color and the z-coordinate be mutually independent. This can be used for 4d data drawing.

Other notes:

1. The term 'scan' referenced above is used more among physicists than the term 'iso_curve' referenced in gnuplot documentation and sources. You measure maps recorded one scan after another scan, that's why.

2. The 'gray' or 'color' scale is a linear mapping of a continuous variable onto a smoothly varying palette of colors. The mapping is shown in a rectangle next to the main plot. This documentation refers to this as a "colorbox", and refers to the indexing variable as lying on the colorbox axis. See `set colorbox`, cbrange.

3. To use pm3d coloring to generate a two-dimensional plot rather than a 3D surface, use `set view map` or `set pm3d map`.

Syntax (the options can be given in any order):

 
      set pm3d {
                 { at <bst combination> }
                 { interpolate <steps in scan>,<steps between scans> }
                 { scansautomatic | scansforward | scansbackward | depthorder }
                 { flush { begin | center | end } }
                 { ftriangles | noftriangles }
                 { clip1in | clip4in }
                 { corners2color { mean|geomean|median|min|max|c1|c2|c3|c4 } }
                 { hidden3d <linestyle> | nohidden3d }
                 { implicit | explicit }
                 { map }
               }
      show pm3d
      unset pm3d

Color surface is drawn if data or function style is set to pm3d globally or via 'with' option, or if the option `implicit` is on--then the pm3d surface is combined with the line surface mesh. See bottom of this section for mode details.

Color surface can be drawn at the base or top (then it is a gray/color planar map) or at z-coordinates of surface points (gray/color surface). This is defined by the `at` option with a string of up to 6 combinations of `b`, `t` and `s`. For instance, `at b` plots at bottom only, `at st` plots firstly surface and then top map, while `at bstbst` will never by seriously used.

Colored quadrangles are plotted one after another. When plotting surfaces (`at s`), the later quadrangles overlap (overdraw) the previous ones. (Gnuplot is not virtual reality tool to calculate intersections of filled polygon meshes.) You may try to switch between `scansforward` and `scansbackward` to force the first scan of the data to be plotted first or last. The default is `scansautomatic` where gnuplot makes a guess about scans order.

If two subsequent scans do not have same number of points, then it has to be decided whether to start taking points for quadrangles from the beginning of both scans (`flush begin`), from their ends (`flush end`) or to center them (`flush center`). Note, that `flush (center|end)` are incompatible with `scansautomatic`: if you specify `flush center` or `flush end` and `scansautomatic` is set, it is silently switched to `scansforward`.

If two subsequent scans do not have the same number of points, the option `ftriangles` specifies whether color triangles are drawn at the scan tail(s) where there are not enough points in either of the scan. This can be used to draw a smooth map boundary.

Clipping with respect to x, y coordinates of quadrangles can be done in two ways. `clip1in`: all 4 points of each quadrangle must be defined and at least 1 point of the quadrangle must lie in the x and y ranges. `clip4in`: all 4 points of each quadrangle must lie in the x and y ranges.

There is a single gray/color value associated to each drawn pm3d quadrangle (no smooth color change among vertices). The value is calculated from z-coordinates from the surrounding corners according to `corners2color <option>`. The options 'mean' (default), 'geomean' and 'median' produce various kinds of surface color smoothing, while options 'min' and 'max' choose minimal or maximal value, respectively. This may not be desired for pixel images or for maps with sharp and intense peaks, in which case the options 'c1', 'c2', 'c3' or 'c4' can be used instead to assign the quadrangle color based on the z-coordinate of only one corner. Some experimentation may be needed to determine which corner corresponds to 'c1', as the orientation depends on the drawing direction. Because the pm3d algorithm does not extend the colored surface outside the range of the input data points, the 'c<j>' coloring options will result in pixels along two edges of the grid not contributing to the color of any quadrangle. For example, applying the pm3d algorithm to the 4x4 grid of data points in script `demo/pm3d.dem` (please have a look) produces only (4-1)x(4-1)=9 colored rectangles.

Another drawing algorithm, which would draw quadrangles around a given node by taking corners from averaged (x,y)-coordinates of its surrounding 4 nodes while using node's color, could be implemented in the future. This is already done for drawing images (2D grids) via `image` and `rgbimage` styles.

Notice that ranges of z-values and color-values for surfaces are adjustable independently by zrange, cbrange, as well as `set log` for z or cb. Maps can be adjusted by the cb-axis only; see also `set view map` and `set colorbox`.

The option hidden3d takes as the argument a linestyle which must be created by `set style line ...`. (The style need not to be present when setting pm3d, but it must be present when plotting). If set, lines are drawn using the specified line style, taking into account hidden line removal. This is by far more efficient than using the command hidden3d as it doesn't really calculate hidden line removal, but just draws the filled polygons in the correct order. So the recommended choice when using pm3d is

 
      set pm3d at s hidden3d 100
      set style line 100 lt 5 lw 0.5
      unset hidden3d
      unset surf
      splot x*x+y*y

There used to be an option {transparent|solid} to this command. Now you get the same effect from `set grid {front|layerdefault}`, respectively.

The `set pm3d map` is an abbreviation for `set pm3d at b`; `set view map`; pm3d; pm3d;. It is used for backwards compatibility, when `set view map` was not available. Take care that you properly use zrange and cbrange for input data point filtering and color range scaling, respectively; and also `set (no)surface` seems to have a (side?) effect.

The option `interpolate` will interpolate grid points into a finer mesh, and color each quadrangle appropriately. For data files, this will smoothen the color surface, and enhance spikes in a color surface. For functions, interpolation makes little sense, except to trade off precision for memory. It would usually make more sense to use samples and isosamples when working with functions.

The coloring setup as well as the color box drawing are determined by palette. There can be only one palette for the current plot. Drawing of several surfaces with different palettes can be achieved by multiplot with fixed origin and size; don't forget to use `set palette maxcolors` when your terminal is running out of available colors.

On gnuplot start-up, mode is `explicit`. For historical and thus compatibility reasons, commands `set pm3d;` (i.e. no options) and `set pm3d at X ...` (i.e. `at` is the first option) sets mode `implicit`. Further, `set pm3d;` sets up the other options to their default.

If the option `implicit` is on, all surface plots will be plotted additionally to the default type, e.g.

 
      splot 'fred.dat' with lines, 'lola.dat' with lines

would give both plots (meshes) additionally to a pm3d surface. That's what you are used to after `set pm3d;`.

If the option `explicit` is on (or `implicit` is off) only plots specified by the pm3d attribute are plotted with a pm3d surface, e.g.:

 
      splot 'fred.dat' with lines, 'lola.dat' with pm3d

would plot 'fred.dat' with lines (and only lines) and 'lola.dat' with a pm3d surface.

If you set the default data or function style to pm3d, e.g.:

 
      set style data pm3d

then the options `implicit` and `explicit` have no effect.

Note that when plotting several plots, they are plotted in the order given on the command line. This can be of interest especially for filled surfaces which can overwrite and therefore hide part of earlier plots.

If pm3d is specified in the `splot` command line, then it accepts the 'at' option. The following plots draw three color surfaces at different altitudes:

 
      set border 4095
      set pm3d at s
      splot 10*x with pm3d at b, x*x-y*y, x*x+y*y with pm3d at t

See also help for palette, cbrange, `set colorbox`, pm3d and definitely the demo file `demo/pm3d.dem`.


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2.21.50 palette

Palette is a color storage for use by pm3d, filled color contours or polygons, color histograms, color gradient background, and whatever it is or it will be implemented... Here it stands for a palette of smooth "continuous" colors or grays, but let's call it just a palette.

Color palettes require terminal entries for filled color polygons and palettes of smooth colors, are currently available for terminals listed in help for pm3d. The range of color values are adjustable independently by cbrange and `set log cb`. The whole color palette is visualized in the `colorbox`.

Syntax:

 
      set palette
      set palette {
                 { gray | color }
                 { gamma <gamma> }
                 {   rgbformulae <r>,<g>,<b>
                   | defined { ( <gray1> <color1> {, <grayN> <colorN>}... ) }
                   | file '<filename>' {datafile-modifiers}
                   | functions <R>,<G>,<B>
                 }
                 { model { RGB | HSV | CMY | YIQ | XYZ } }
                 { positive | negative }
                 { nops_allcF | ps_allcF }
                 { maxcolors <maxcolors> }
               }
      show palette
      show palette palette <n> {{float | int}}
      show palette gradient
      show palette fit2rgbformulae
      show palette rgbformulae
      show palette colornames

palette (i.e. without options) sets up the default values. Otherwise, the options can be given in any order. palette shows the current palette properties.

`show palette gradient` displays the gradient defining the palette (if appropriate). rgbformulae prints the available fixed gray -> color transformation formulae. colornames prints the implemented color names.

`show palette palette <n>` prints to screen or to the file given by output table of RGB triplets calculated for the current palette settings and a palette having <n> discrete colors. The default wide table can be limited to 3 columns of r,g,b float values [0..1] or integer values [0..255] by options float or int, respectively. This way, the current gnuplot color palette can be loaded into other imaging applications, for example Octave. Additionally to this textual list of RGB table, you can enjoy command palette to draw graphically the R,G,B profiles for the current palette.

The following options determine the coloring properties.

Figure using this palette can be `gray` or `color`. For instance, in pm3d color surfaces the gray of each small spot is obtained by mapping the averaged z-coordinate of the 4 corners of surface quadrangles into the range [min_z,max_z] providing range of grays [0:1]. This value can be used directly as the gray for gray maps. The color map requires a transformation gray -> (R,G,B), i.e. a mapping [0:1] -> ([0:1],[0:1],[0:1]).

Basically two different types of mappings can be used: Analytic formulae to convert gray to color, or discrete mapping tables which are interpolated. rgbformulae and `palette functions` use analytic formulae whereas `palette defined` and file use interpolated tables. rgbformulae reduces the size of postscript output to a minimum.

The command `show palette fit2rgbformulae` finds the best matching rgbformulae for the current palette. Naturally, it makes sense to use it for non-rgbformulae palettes. This command can be found useful mainly for external programs using the same rgbformulae definition of palettes as gnuplot, like zimg ( http://zimg.sourceforge.net

 
 ).

`set palette gray` switches to a gray only palette. rgbformulae, `set palette defined`, file and `set palette functions` switch to a color mapping. `set palette color` is an easy way to switch back from the gray palette to the last color mapping.

Automatic gamma correction via `set palette gamma <gamma>` can be done for gray maps only (`set palette gray`). Linear mapping to gray is for gamma equals 1, see palette. Gamma is ignored for color mappings.

Most terminals support only discrete number of colors (e.g. 256 colors in gif). All entries of the palette remaining after the default gnuplot linetype colors declaration are allocated for pm3d by default. Then multiplot could fail if there are no more color positions in the terminal available. Then you should use `set palette maxcolors <maxcolors>` with a reasonably small value. This option can also be used to separate levels of z=constant in discrete steps, thus to emulate filled contours. Default value of 0 stays for allocating all remaining entries in the terminal palette or for to use exact mapping to RGB.

RGB color space might not be the most useful color space to work in. For that reason you may change the color space with `model` to one of `RGB`, `HSV`, `CMY`, `YIQ` and `XYZ`. Using color names for `set palette defined` tables and a color space other than RGB will result in funny colors. All explanation have been written for RGB color space, so please note, that `R` can be `H`, `C`, `Y`, or `X`, depending on the actual color space (`G` and `B` accordingly).

All values for all color spaces are limited to [0,1].

RGB stands for Red, Green and Blue; CMY stands for Cyan, Magenta and Yellow; HSV stands for Hue, Saturation, and Value; YIQ is the color model used by the U.S. Commercial Color Television Broadcasting, it is basically an RGB recoding with downward compatibility for black and white television; XYZ are the three primary colors of the color model defined by the 'Commission Internationale de l'Eclairage' (CIE). For more information on color models see: http://www.cs.rit.edu/~ncs/color/glossary.htm and http://cs.fit.edu/wds/classes/cse5255/cse5255/davis/index.html


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2.21.50.1 rgbformulae

For rgbformulae three suitable mapping functions have to be chosen. This is done via `rgbformulae <r>,<g>,<b>`. The available mapping functions are listed by rgbformulae. Default is `7,5,15`, some other examples are `3,11,6`, `21,23,3` or `3,23,21`. Negative numbers, like `3,-11,-6`, mean inverted color (i.e. 1-gray passed into the formula, see also `positive` and `negative` options below).

Some nice schemes in RGB color space

 
   7,5,15   ... traditional pm3d (black-blue-red-yellow)
   3,11,6   ... green-red-violet
   23,28,3  ... ocean (green-blue-white); try also all other permutations
   21,22,23 ... hot (black-red-yellow-white)
   30,31,32 ... color printable on gray (black-blue-violet-yellow-white)
   33,13,10 ... rainbow (blue-green-yellow-red)
   34,35,36 ... AFM hot (black-red-yellow-white)

A full color palette in HSV color space

 
   3,2,2    ... red-yellow-green-cyan-blue-magenta-red

Please note that even if called rgbformulae the formulas might actually determine the <H>,<S>,<V> or <X>,<Y>,<Z> or ... color components as usual.

Use `positive` and `negative` to invert the figure colors.

Note that it is possible to find a set of the best matching rgbformulae for any other color scheme by the command

 
   show palette fit2rgbformulae


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2.21.50.2 defined

Gray-to-rgb mapping can be manually set by use of `palette defined`: A color gradient is defined and used to give the rgb values. Such a gradient is a piecewise linear mapping from gray values in [0,1] to the RGB space [0,1]x[0,1]x[0,1]. You have to specify the gray values and the corresponding RGB values in between a linear interpolation shall take place:

Syntax:

 
      set palette  defined { ( <gray1> <color1> {, <grayN> <colorN>}... ) }

<grayX> are gray values which are mapped to [0,1] and <colorX> are the corresponding rgb colors. The color can be specified in three different ways:

 
     <color> :=  { <r> <g> <b> | '<color-name>' | '#rrggbb' }

Either by three numbers (each in [0,1]) for red, green and blue, separated by whitespace, or the name of the color in quotes or X style color specifiers also in quotes. You may freely mix the three types in a gradient definition, but the named color "red" will be something strange if RGB is not selected as color space. Use colornames for a list of known color names.

Please note, that even if written as <r>, this might actually be the <H> component in HSV color space or <X> in CIE-XYZ space, or ... depending on the selected color model.

The <gray> values have to form an ascending sequence of real numbers; the sequence will be automatically rescaled to [0,1].

`set palette defined` (without a gradient definition in braces) switches to RGB color space and uses a preset full-spectrum color gradient. Use `show palette gradient` to display the gradient.

Examples:

To produce a gray palette (useless but instructive) use:

 
      set palette model RGB
      set palette defined ( 0 "black", 1 "white" )

To produce a blue yellow red palette use (all equivalent):

 
      set palette defined ( 0 "blue", 1 "yellow", 2 "red" )
      set palette defined ( 0 0 0 1, 1 1 1 0, 2 1 0 0 )
      set palette defined ( 0 "#0000ff", 1 "#ffff00", 2 "#ff0000" )

To produce some rainbow-like palette use:

 
      set palette defined ( 0 "blue", 3 "green", 6 "yellow", 10 "red" )

Full color spectrum within HSV color space:

 
      set palette model HSV
      set palette defined ( 0 0 1 1, 1 1 1 1 )
      set palette defined ( 0 0 1 0, 1 0 1 1, 6 0.8333 1 1, 7 0.8333 0 1)

To produce a palette with few colors only use:

 
      set palette model RGB maxcolors 4
      set palette defined ( 0 "blue", 1 "green", 2 "yellow", 3 "red" )

'Traffic light' palette (non-smooth color jumps at gray = 1/3 and 2/3).

 
      set palette model RGB
      set palette defined (0 "dark-green", 1 "green", 1 "yellow", \
                           2 "dark-yellow", 2 "red", 3 "dark-red" )


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2.21.50.3 functions

Use `set palette functions <Rexpr>, <Gexpr>, <Bexpr>` to define three formulae for the R(gray), G(gray) and B(gray) mapping. The three formulae may depend on the variable `gray` which will take values in [0,1] and should also produce values in [0,1]. Please note that <Rexpr> might be a formula for the H-value if HSV color space has been chosen (same for all other formulae and color spaces).

Examples:

To produce a full color palette use:

 
      set palette model HSV functions gray, 1, 1

A nice black to gold palette:

 
      set palette model XYZ functions gray**0.35, gray**0.5, gray**0.8

A gamma-corrected black and white palette

 
      gamma = 2.2
      color(gray) = gray**(1./gamma)
      set palette model RGB functions color(gray), color(gray), color(gray)


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2.21.50.4 file

file is basically a `set palette defined (<gradient>)` where <gradient> is read from a datafile. Either 4 columns (gray,R,G,B) or just three columns (R,G,B) have to be selected via the using data file modifier. In the three column case, the line number will be used as gray. The gray range is automatically rescaled to [0,1]. The file is read as a normal data file, so all datafile modifiers can be used. Please note, that `R` might actually be e.g. `H` if HSV color space is selected.

As usual <filename> may be `'-'` which means that the data follow the command inline and are terminated by a single `e` on a line of its own.

Use `show palette gradient` to display the gradient.

Examples:

Read in a palette of RGB triples each in range [0,255]:

 
      set palette file 'some-palette' using ($1/255):($2/255):($3/255)

Equidistant rainbow (blue-green-yellow-red) palette:

 
      set palette model RGB file "-"
      0 0 1
      0 1 0
      1 1 0
      1 0 0
      e

Binary palette files are supported as well, see `binary general`. Example: put 64 triplets of R,G,B doubles into file palette.bin and load it by

 
      set palette file "palette.bin" binary record=64 using 1:2:3


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2.21.50.5 gamma correction

For gray mappings gamma correction can be turned on by `set palette gamma <gamma>`. <gamma> defaults to 1.5 which is quite suitable for most terminals.

For color mappings no automatic gamma correction is done by gnuplot. However, you may easily implement gamma correction. Here is an example for a gray scale image by use of explicit functions for the red, green and blue component with slightly different values of gamma

Example:

 
      set palette model RGB
      set palette functions gray**0.64, gray**0.67, gray**0.70

To use gamma correction with interpolated gradients specify intermediate gray values with appropriate colors. Instead of

 
      set palette defined ( 0 0 0 0, 1 1 1 1 )

use e.g.

 
      set palette defined ( 0 0 0 0, 0.5 .73 .73 .73, 1 1 1 1 )

or even more intermediate points until the linear interpolation fits the "gamma corrected" interpolation well enough.


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2.21.50.6 postscript

In order to reduce the size of postscript files, the gray value and not all three calculated r,g,b values are written to the file. Therefore the analytical formulae are coded directly in the postscript language as a header just before the pm3d drawing, see /g and /cF definitions. Usually, it makes sense to write therein definitions of only the 3 formulae used. But for multiplot or any other reason you may want to manually edit the transformations directly in the postscript file. This is the default option `nops_allcF`. Using the option `ps_allcF` writes postscript definitions of all formulae. This you may find interesting if you want to edit the postscript file in order to have different palettes for different surfaces in one graph. Well, you can achieve this functionality by multiplot with fixed origin and size.

If pm3d map has been plotted from gridded or almost regular data with an output to a postscript file, then it is possible to reduce the size of this postscript file up to at about 50% by the enclosed awk script `pm3dCompress.awk`. This you may find interesting if you intend to keep the file for including it into your publication or before downloading a very large file into a slow printer. Usage:

 
    awk -f pm3dCompress.awk thefile.ps >smallerfile.ps

If pm3d map has been plotted from rectangular gridded data with an output to a postscript file, then it is possible to reduce the file size even more by the enclosed awk script `pm3dConvertToImage.awk`. Usage:

 
    awk -f pm3dConvertToImage.awk <thefile.ps >smallerfile.ps

You may manually change the postscript output from gray to color and vice versa and change the definition of <maxcolors>.


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2.21.50.7 colornames

Gnuplot knows a limited number of color names. You can use these to define the color range spanned by a pm3d palette, or to assign a terminal-independent colot to a particular linetype or linestyle. To see the list of know color names, use the command colornames. See palette, `linestyle`.


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2.21.51 pointsize

The pointsize command scales the size of the points used in plots.

Syntax:

 
      set pointsize <multiplier>
      show pointsize

The default is a multiplier of 1.0. Larger pointsizes may be useful to make points more visible in bitmapped graphics.

The pointsize of a single plot may be changed on the `plot` command. See with for details.

Please note that the pointsize setting is not supported by all terminal types.


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2.21.52 polar

The `set polar` command changes the meaning of the plot from rectangular coordinates to polar coordinates.

Syntax:

 
      set polar
      unset polar
      show polar

There have been changes made to polar mode in version 3.7, so that scripts for `gnuplot` versions 3.5 and earlier will require modification. The main change is that the dummy variable t is used for the angle so that the x and y ranges can be controlled independently. Other changes are: 1) tics are no longer put along the zero axes automatically --use `set xtics axis nomirror`; `set ytics axis nomirror`; 2) the grid, if selected, is not automatically polar --use `set grid polar`; 3) the grid is not labelled with angles --use label as necessary.

In polar coordinates, the dummy variable (t) is an angle. The default range of t is [0:2*pi], or, if degree units have been selected, to [0:360] (see angles).

The command `unset polar` changes the meaning of the plot back to the default rectangular coordinate system.

The `set polar` command is not supported for `splot`s. See the mapping command for similar functionality for `splot`s.

While in polar coordinates the meaning of an expression in t is really r = f(t), where t is an angle of rotation. The trange controls the domain (the angle) of the function, and the x and y ranges control the range of the graph in the x and y directions. Each of these ranges, as well as the rrange, may be autoscaled or set explicitly. See xrange for details of all the ranges commands.

Example:

 
      set polar
      plot t*sin(t)
      plot [-2*pi:2*pi] [-3:3] [-3:3] t*sin(t)

The first `plot` uses the default polar angular domain of 0 to 2*pi. The radius and the size of the graph are scaled automatically. The second `plot` expands the domain, and restricts the size of the graph to [-3:3] in both directions.

You may want to `set size square` to have `gnuplot` try to make the aspect ratio equal to unity, so that circles look circular. See also polar demos (polar.dem) and polar data plot (poldat.dem).


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2.21.53 print

The `set print` command redirects the output of the `print` command to a file.

Syntax:

 
      set print
      set print "-"
      set print "<filename>"
      set print "<filename>" append
      set print "|<shell_command>"

Without "<filename>", the output file is restored to <STDERR>. The <filename> "-" means <STDOUT>. The `append` flag causes the file to be opened in append mode. A <filename> starting with "|" is opened as a pipe to the <shell_command> on platforms that support piping.


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2.21.54 object

This command defines a single object, which will appear in all subsequent 2D plots. You may define as many objects as you like. Currently the only object type supported is `rectangle`. Each rectangle is specified by a pair of points that define diagonal vertices. A default set of style properties (fill, color, border) are inherited from those set by the command `set style rectangle`, but each rectangle can also be given individual style properties.

Syntax:

 
    set object <index> rectangle
        {from <position> {to|rto} <position> |
         center <position> size <w>,<h> |
         at <position> size <w>,<h>}
        {front|back|behind} {fc|fillcolor <colorspec>} {fs <fillstyle>}
        {default} {lw|linewidth <width>}

The position of the rectangle may be specified by giving the position of two diagonal corners (bottom left and top right) or by giving the position of the center followed by the width and the height. In either case the positions may be given in axis, graph, or screen coordinates. See `coordinates`. The options `at` and `center` are synonyms.

Setting `front` will draw the rectangle in front of all plot elements, but behind any labels that are also marked `front`. Setting `back` will place the rectangle behind all plot curves and labels. Setting `behind` will place the rectangle behind everything including the axes and `back` rectangles, and can be used to provide a colored background for the entire graph or page.

The fill color of the rectangle is taken from the <colorspec>. `fillcolor` may be abbreviated `fc`. The fill style is taken from <fillstyle>. See colorspec and `fillstyle`. If the keyword `default` is given, these properties are inherited from the default settings of at the time a plot is drawn. See `set style rectangle`.

Examples:

 
    # Force the entire area enclosed by the axes to have background color cyan
    set object 1 rect from graph 0, graph 0 to graph 1, graph 1 back
    set object 1 rect fc rgb "cyan" fillstyle solid 1.0

 
    # Position a red square with lower left at 0,0 and upper right at 2,3
    set object 2 rect from 0,0 to 2,3 fc lt 1

 
    # Position an empty rectangle (no fill) with a blue border
    set object 3 rect from 0,0 to 2,3 fs empty border 3

 
    # Return fill and color to the default style but leave vertices unchanged
    set object 2 rect default


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2.21.55 rmargin

The command rmargin sets the size of the right margin. Please see margin for details.


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2.21.56 rrange

The rrange command sets the range of the radial coordinate for a graph in polar mode. Please see xrange for details.


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2.21.57 samples

The sampling rate of functions, or for interpolating data, may be changed by the samples command.

Syntax:

 
      set samples <samples_1> {,<samples_2>}
      show samples

By default, sampling is set to 100 points. A higher sampling rate will produce more accurate plots, but will take longer. This parameter has no effect on data file plotting unless one of the interpolation/approximation options is used. See smooth re 2-d data and cntrparam and dgrid3d re 3-d data.

When a 2-d graph is being done, only the value of <samples_1> is relevant.

When a surface plot is being done without the removal of hidden lines, the value of samples specifies the number of samples that are to be evaluated for the isolines. Each iso-v line will have <sample_1> samples and each iso-u line will have <sample_2> samples. If you only specify <samples_1>, <samples_2> will be set to the same value as <samples_1>. See also isosamples.


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2.21.58 size

Syntax:

 
      set size {{no}square | ratio <r> | noratio} {<xscale>,<yscale>}
      show size

The <xscale> and <yscale> values are scale factors for the size of the plot, which includes the graph, labels, and margins.

Important note:

 
      In earlier versions of gnuplot, some terminal types used the values from
      size to control also the size of the output canvas; others did not.
      In version 4.2 almost all terminals now follow the following convention:

`set term <terminal_type> size <XX>, <YY>` controls the size of the output file, or `canvas`. Please see individual terminal documentation for allowed values of the size parameters. By default, the plot will fill this canvas.

`set size <XX>, <YY>` scales the plot itself relative to the size of the canvas. Scale values less than 1 will cause the plot to not fill the entire canvas. Scale values larger than 1 will cause only a portion of the plot to fit on the canvas. Please be aware that setting scale values larger than 1 may cause problems on some terminal types.

`ratio` causes `gnuplot` to try to create a graph with an aspect ratio of <r> (the ratio of the y-axis length to the x-axis length) within the portion of the plot specified by <xscale> and <yscale>.

The meaning of a negative value for <r> is different. If <r>=-1, gnuplot tries to set the scales so that the unit has the same length on both the x and y axes (suitable for geographical data, for instance). If <r>=-2, the unit on y has twice the length of the unit on x, and so on.

The success of `gnuplot` in producing the requested aspect ratio depends on the terminal selected. The graph area will be the largest rectangle of aspect ratio <r> that will fit into the specified portion of the output (leaving adequate margins, of course).

`square` is a synonym for `ratio 1`.

Both `noratio` and `nosquare` return the graph to the default aspect ratio of the terminal, but do not return <xscale> or <yscale> to their default values (1.0).

`ratio` and `square` have no effect on 3-d plots.

Examples:

To set the size so that the plot fills the available canvas:

 
      set size 1,1

To make the graph half size and square use:

 
      set size square 0.5,0.5

To make the graph twice as high as wide use:

 
      set size ratio 2

See also airfoil demo.


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2.21.59 style

Default plotting styles are chosen with the `set style data` and `set style function` commands. See with for information about how to override the default plotting style for individual functions and data sets. See `plotting styles` for a complete list of styles.

Syntax:

 
      set style function <style>
      set style data <style>
      show style function
      show style data

Default styles for specific plotting elements may also be set.

Syntax:

 
      set style arrow <n> <arrowstyle>
      set style fill <fillstyle>
      set style histogram <histogram style options>
      set style line <n> <linestyle>


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2.21.59.1 set style arrow

Each terminal has a default set of arrow and point types, which can be seen by using the command test. arrow defines a set of arrow types and widths and point types and sizes so that you can refer to them later by an index instead of repeating all the information at each invocation.

Syntax:

 
      set style arrow <index> default
      set style arrow <index> {nohead | head | heads}
                              {size <length>,<angle>{,<backangle>}}
                              {filled | empty | nofilled}
                              {front | back}
                              { {linestyle | ls <line_style>}
                                | {linetype | lt <line_type>}
                                  {linewidth | lw <line_width} }
      unset style arrow
      show style arrow

<index> is an integer that identifies the arrowstyle.

If `default` is given all arrow style parameters are set to their default values.

If the linestyle <index> already exists, only the given parameters are changed while all others are preserved. If not, all undefined values are set to the default values.

Specifying `nohead` produces arrows drawn without a head--a line segment. This gives you yet another way to draw a line segment on the plot. By default, arrows have one head. Specifying `heads` draws arrow heads on both ends of the line.

Head size can be controlled by `size <length>,<angle>` or `size <length>,<angle>,<backangle>`, where `<length>` defines length of each branch of the arrow head and `<angle>` the angle (in degrees) they make with the arrow. `<Length>` is in x-axis units; this can be changed by `first`, `second`, `graph`, `screen`, or `character` before the <length>; see `coordinates` for details. `<Backangle>` only takes effect when `filled` or `empty` is also used. Then, `<backangle>` is the angle (in degrees) the back branches make with the arrow (in the same direction as `<angle>`). The `fig` terminal has a restricted backangle function. It supports three different angles. There are two thresholds: Below 70 degrees, the arrow head gets an indented back angle. Above 110 degrees, the arrow head has an acute back angle. Between these thresholds, the back line is straight.

Specifying `filled` produces filled arrow heads (if heads are used). Filling is supported on filled-polygon capable terminals, see help of pm3d for their list, otherwise the arrow heads are closed but not filled. The same result (closed but not filled arrow head) is reached by specifying `empty`. Further, filling and outline is obviously not supported on terminals drawing arrows by their own specific routines, like `metafont`, `metapost`, `latex` or `tgif`.

The line style may be selected from a user-defined list of line styles (see `set style line`) or may be defined here by providing values for `<line_type>` (an index from the default list of styles) and/or `<line_width>` (which is a multiplier for the default width).

Note, however, that if a user-defined line style has been selected, its properties (type and width) cannot be altered merely by issuing another arrow command with the appropriate index and `lt` or `lw`.

If `front` is given, the arrows are written on top of the graphed data. If `back` is given (the default), the arrow is written underneath the graphed data. Using `front` will prevent a arrow from being obscured by dense data.

Examples:

To draw an arrow without an arrow head and double width, use:

 
      set style arrow 1 nohead lw 2
      set arrow arrowstyle 1

 
 See also arrow for further examples.


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2.21.59.2 set style data

The `set style data` command changes the default plotting style for data plots.

Syntax:

 
      set style data <plotting-style>
      show style data

See `plotting styles` for the choices. If no choice is given, the choices are listed. `show style data` shows the current default data plotting style.


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2.21.59.3 set style fill

The `set style fill` command is used to set the style of boxes, histograms, candlesticks and filledcurves.

Syntax:

 
      set style fill {empty | solid {<density>} | pattern {<n>}}
                     {border {<linetype>} | noborder}

The default fillstyle is `empty`.

The `solid` option causes filling with a solid color, if the terminal supports that. The <density> parameter specifies the intensity of the fill color. At a <density> of 0.0, the box is empty, at <density> of 1.0, the inner area is of the same color as the current linetype. Some terminal types can vary the density continuously; others implement only a few levels of partial fill. If no <density> parameter is given, it defaults to 1.

The `pattern` option causes filling to be done with a fill pattern supplied by the terminal driver. The kind and number of available fill patterns depend on the terminal driver. If multiple datasets using filled boxes are plotted, the pattern cycles through all available pattern types, starting from pattern <n>, much as the line type cycles for multiple line plots.

The `empty` option causes filled boxes not to be filled. This is the default. It is equivalent to the `solid` option with a <density> parameter of zero.

By default, border, the box is bounded by a solid line of the current linetype. `border <lt>` specifies that a border is to be drawn using linetype <lt>. `noborder` specifies that no bounding lines are drawn.


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2.21.59.4 set style function

The `set style function` command changes the default plotting style for function plots.

Syntax:

 
      set style function <plotting-style>
      show style function

See `plotting styles` for the choices. If no choice is given, the choices are listed. `show style function` shows the current default function plotting style.


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2.21.59.5 set style increment

Syntax:

 
      set style increment {default|userstyles}
      show style increment

By default, successive plots within the same graph will use successive linetypes from the default set for the current terminal type. However, choosing `set style increment user` allows you to step through the user-defined line styles rather than through the default linetypes.

Example:

 
      set style line 1 lw 2 lc rgb "gold"
      set style line 2 lw 2 lc rgb "purple"
      set style line 4 lw 1 lc rgb "sea-green"
      set style increment user

 
      plot f1(x), f2(x), f3(x), f4(x)

should plot functions f1, f2, f4 in your 3 newly defined line styles. If a user-defined line style is not found then the corresponding default linetype is used instead. E.g. in the example above, f3(x) will be plotted using the default linetype 3.


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2.21.59.6 set style line

Each terminal has a default set of line and point types, which can be seen by using the command test. `set style line` defines a set of line types and widths and point types and sizes so that you can refer to them later by an index instead of repeating all the information at each invocation.

Syntax:

 
      set style line <index> default
      set style line <index> {{linetype  | lt} <line_type> | <colorspec>}
                             {{linecolor | lc} <colorspec>}
                             {{linewidth | lw} <line_width>}
                             {{pointtype | pt} <point_type>}
                             {{pointsize | ps} <point_size>}
                             {palette}
      unset style line
      show style line

If `default` is given all line style parameters are set to their default values.

If the linestyle <index> already exists, only the given parameters are changed while all others are preserved. If not, all undefined values are set to the default values.

The line and point types are taken from the default types for the terminal currently in use. The line width and point size are multipliers for the default width and size (but note that <point_size> here is unaffected by the multiplier given on pointsize).

The defaults for the line and point types is the index. The defaults for the width and size are both unity.

Linestyles created by this mechanism do not replace the default linetype styles; both may be used. If you want plots to use the defined styles in preference to the default linetypes, please see `set style increment`.

Not all terminals support the `linewidth` and pointsize features; if not supported, the option will be ignored.

Terminal-independent colors may be assigned using either `linecolor <colorspec>` or `linetype <colorspec>`, abbreviated `lc` or `lt`. This requires giving a RGB color triple, a known palette color name, a fractional index into the current palette, or a constant value from the current mapping of the palette onto cbrange. See `colors`, colorspec, palette, colornames, cbrange.

`set style line <n> linetype <lt>` will set both a terminal-dependent dot/dash pattern and color. The commands`set style line <n> linecolor <colorspec>` or `set style line <n> linetype <colorspec>` will set a new line color while leaving the existing dot-dash pattern unchanged.

In 3d mode (`splot` command), the special keyword palette is allowed as a shorthand for "linetype palette z". The color value corresponds to the z-value (elevation) of the splot, and varies smoothly along a line or surface.

Examples: Suppose that the default lines for indices 1, 2, and 3 are red, green, and blue, respectively, and the default point shapes for the same indices are a square, a cross, and a triangle, respectively. Then

 
      set style line 1 lt 2 lw 2 pt 3 ps 0.5

defines a new linestyle that is green and twice the default width and a new pointstyle that is a half-sized triangle. The commands

 
      set style function lines
      plot f(x) lt 3, g(x) ls 1

will create a plot of f(x) using the default blue line and a plot of g(x) using the user-defined wide green line. Similarly the commands

 
      set style function linespoints
      plot p(x) lt 1 pt 3, q(x) ls 1

will create a plot of p(x) using the default triangles connected by a red line and q(x) using small triangles connected by a green line.

 
      splot sin(sqrt(x*x+y*y))/sqrt(x*x+y*y) w l pal

creates a surface plot using smooth colors according to palette. Note, that this works only on some terminals. See also palette, pm3d.

 
      set style line 10 linetype 1 linecolor rgb "cyan"

will assign linestyle 10 to be a solid cyan line on any terminal that supports rgb colors.


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2.21.59.7 plotting styles

The commands `set style data` and `set style function` change the default plotting style for subsequent `plot` and `splot` commands.

The types used for all line and point styles (i.e., solid, dash-dot, color, etc. for lines; circles, squares, crosses, etc. for points) will be either those specified on the `plot` or `splot` command or will be chosen sequentially from the types available to the terminal in use. Use the command test to see what is available.

None of the styles requiring more than two columns of information (e.g., errorbars or errorlines) can be used with `splot`s or function `plot`s. Neither `boxes`, `filledcurves` nor any of the `steps` styles can be used with `splot`s. If an inappropriate style is specified, it will be changed to `points`.

The above caveat does not apply to `plot with labels`, for which the third column specifies a data source rather than coordinate information. See `set style labels`.

For 2-d data with more than two columns, `gnuplot` is picky about the allowed errorbars and errorlines styles. The using option on the `plot` command can be used to set up the correct columns for the style you want. (In this discussion, "column" will be used to refer both to a column in the data file and an entry in the using list.)

For three columns, only `xerrorbars`, `yerrorbars` (or errorbars), `xerrorlines`, `yerrorlines` (or errorlines), `boxes`, and `boxerrorbars` are allowed. If another plot style is used, the style will be changed to `yerrorbars`. The `boxerrorbars` style will calculate the boxwidth automatically.

For four columns, only `xerrorbars`, `yerrorbars` (or errorbars), `xyerrorbars`, `xerrorlines`, `yerrorlines` (or errorlines), `xyerrorlines`, `boxxyerrorbars`, and `boxerrorbars` are allowed. An illegal style will be changed to `yerrorbars`.

Five-column data allow only the `boxerrorbars`, `financebars`, and `candlesticks` styles. An illegal style will be changed to `boxerrorbars` before plotting.

Six- and seven-column data only allow the `xyerrorbars`, `xyerrorlines`, and `boxxyerrorbars` styles. Illegal styles will be changed to `xyerrorbars` before plotting.

For more information about error bars with and without lines, please see errorlines and errorbars.


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2.21.59.8 set style rectangle

Rectangles defined with the `set object rectangle` command can have individual styles. However, if a rectangle is not assigned a private style then it inherits a default that is taken from the `set style rectangle` command.

Syntax:

 
    set style rectangle {front|back} {fillcolor <colorspec>} {fs <fillstyle>}
                        {lw|linewidth <lw>}

See colorspec and `fillstyle`. `fillcolor` may be abbreviated as `fc`.

Examples:

 
    set style rectangle back fc rgb "white" fs solid 1.0 border -1
    set style rectangle fc linsestyle 3 fs pattern 2 noborder

The default values correspond to solid fill with the background color and a black border.

-- BOXERRORBARS --

The `boxerrorbars` style is only relevant to 2-d data plotting. It is a combination of the `boxes` and `yerrorbars` styles. The boxwidth will come from the fourth column if the y errors are in the form of "ydelta" and the boxwidth was not previously set equal to -2.0 (`set boxwidth -2.0`) or from the fifth column if the y errors are in the form of "ylow yhigh". The special case `boxwidth = -2.0` is for four-column data with y errors in the form "ylow yhigh". In this case the boxwidth will be calculated so that each box touches the adjacent boxes. The width will also be calculated in cases where three-column data are used.

The box height is determined from the y error in the same way as it is for the `yerrorbars` style--either from y-ydelta to y+ydelta or from ylow to yhigh, depending on how many data columns are provided. See also errorbar demo.

-- BOXES --

The `boxes` style is only relevant to 2-d plotting. It draws a box centered about the given x coordinate from the x axis (not the graph border) to the given y coordinate. The width of the box is obtained in one of three ways. If it is a data plot and the data file has a third column, this will be used to set the width of the box. If not, if a width has been set using the boxwidth command, this will be used. If neither of these is available, the width of each box will be calculated automatically so that it touches the adjacent boxes.

The interior of the boxes is drawn according to the current fillstyle. See `set style fill` for details. Alternatively a new fillstyle may be specified in the plot command.

For fillstyle `empty` the box is filled with the background color.

For fillstyle `solid` the box is filled with a solid rectangle of the current drawing color. There is an optional parameter <density> that controls the fill density; it runs from 0 (background color) to 1 (current drawing color).

For fillstyle `pattern` the box is filled in the current drawing color with a pattern, if supported by the terminal driver.

Examples:

To plot a data file with solid filled boxes with a small vertical space separating them (bargraph):

 
      set boxwidth 0.9 relative
      set style fill solid 1.0
      plot 'file.dat' with boxes

To plot a sine and a cosine curve in pattern-filled boxes style:

 
      set style fill pattern
      plot sin(x) with boxes, cos(x) with boxes

The sin plot will use pattern 0; the cos plot will use pattern 1. Any additional plots would cycle through the patterns supported by the terminal driver.

To specify explicit fillstyles for each dataset:

 
     plot 'file1' with boxes fs solid 0.25, \
          'file2' with boxes fs solid 0.50, \
          'file3' with boxes fs solid 0.75, \
          'file4' with boxes fill pattern 1, \
          'file5' with boxes fill empty

Currently only the following terminal drivers support fillstyles other than `empty`: x11, windows, pm, wxt, postscript, fig, pbm, png, gif, hpdj, hppj, hpljii, hp500c, jpeg, nec_cp6, epson_180dpi, epson_60dpi, epson_lx800, okidata, starc and tandy_60dpi. The BeOS driver (`be`) is untested.

-- BOXXYERRORBARS --

The `boxxyerrorbars` style is only relevant to 2-d data plotting. It is a combination of the `boxes` and `xyerrorbars` styles.

The box width and height are determined from the x and y errors in the same way as they are for the `xyerrorbars` style--either from xlow to xhigh and from ylow to yhigh, or from x-xdelta to x+xdelta and from y-ydelta to y+ydelta , depending on how many data columns are provided.

If filled-box support is present, then the interior of the boxes is drawn according to the current fillstyle. See `set style fill` and `boxes` for details. Alternatively a new fillstyle may be specified in the plot command.

-- CANDLESTICKS --

The `candlesticks` style can be used for 2-d data plotting of financial data or for generating box-and-whisker plots of statistical data. Five columns of data are required; in order, these should be the x coordinate (most likely a date) and the opening, low, high, and closing prices. The symbol is a rectangular box, centered horizontally at the x coordinate and limited vertically by the opening and closing prices. A vertical line segment at the x coordinate extends up from the top of the rectangle to the high price and another down to the low. The vertical line will be unchanged if the low and high prices are interchanged.

The width of the rectangle can be controlled by the boxwidth command. For backwards compatibility with earlier gnuplot versions, when the boxwidth parameter has not been set then the width of the candlestick rectangle is controlled by `set bars <width>`.

By default the vertical line segments have no crossbars at the top and bottom. If you want crossbars, which are typically used for box-and-whisker plots, then add the keyword `whiskerbars` to the plot command. By default these whiskerbars extend the full horizontal width of the candlestick, but you can modify this by specifying a fraction of the full width.

By default the rectangle is empty if (open > close), and filled with three vertical bars if (close > open). If filled-boxes support is present, then the rectangle is colored according to `set style fill <fillstyle>`. See bars and `financebars`. See also finance demos .

Note: To place additional symbols, such as the median value, on a box-and-whisker plot requires additional plot commands as in this example:

 
  # Data columns: X Min 1stQuartile Median 3rdQuartile Max
  set bars 4.0
  set style fill empty
  plot 'stat.dat' using 1:3:2:6:5 with candlesticks title 'Quartiles', \
       ''         using 1:4:4:4:4 with candlesticks lt -1 notitle

 
  # Plot with crossbars on the whiskers, crossbars are 50% of full width
  plot 'stat.dat' using 1:3:2:6:5 with candlesticks whiskerbars 0.5

 
 See boxwidth, bars and `set style fill`.

-- DOTS --

The `dots` style plots a tiny dot at each point; this is useful for scatter plots with many points. For some terminals (post, pdf) the size of the dot can be controlled by changing the linewidth.

-- FILLEDCURVES --

The `filledcurves` style is only relevant to 2-d plotting. Three variants are possible. The first two variants require either a function or two columns of input data, and may be further modified by the options listed below. The first variant, `closed`, treats the curve itself as a closed polygon. This is the default if there are two columns of input data.

The second variant is to fill the area between the curve and a given axis, a horizontal or vertical line, or a point.

The third variant requires three columns of input data: the x coordinate and two y coordinates corresponding to two curves sampled at the same set of x coordinates; the area between the two curves is filled. This is the default if there are three or more columns of input data.

Syntax:

 
    set style [data | function] filledcurves [option]
    plot ... with filledcurves [option]

where the option can be

 
    [closed | {above | below} {x1 | x2 | y1 | y2}[=<a>] | xy=<x>,<y>]

The first two plot variants can be further modified by the options

 
    filledcurves closed   ... just filled closed curve,
    filledcurves x1       ... x1 axis,
    filledcurves x2       ... x2 axis, etc for y1 and y2 axes,
    filledcurves y1=0     ... line y=0 (at y1 axis) ie parallel to x1 axis,
    filledcurves y2=42    ... line y=42 (at y2 axis) ie parallel to x2, etc,
    filledcurves xy=10,20 ... point 10,20 of x1,y1 axes (arc-like shape).

Example of filling the area between two input curves. fill between curves demo.

 
    plot 'data' using 1:2:3 with filledcurves

The `above` and `below` options apply both to commands of the form

 
    ... filledcurves above {x1|x2|y1|y2}=<val>

and to commands of the form

 
    ... using 1:2:3 with filledcurves below

In either case the option limits the filled area to one side of the bounding line or curve.

Note: Not all terminal types support this plotting mode.

Zoom of a filled curve drawn from a datafile may produce empty or incorrect area because gnuplot is clipping points and lines, and not areas.

If the values of <a>, <x>, <y> are out of the drawing boundary, then they are moved to the graph boundary. Then the actually filled area in the case of option xy=<x>,<y> will depend on xrange and yrange.

-- FINANCEBARS --

The `financebars` style is only relevant for 2-d data plotting of financial data. Five columns of data are required; in order, these should be the x coordinate (most likely a date) and the opening, low, high, and closing prices. The symbol is a vertical line segment, located horizontally at the x coordinate and limited vertically by the high and low prices. A horizontal tic on the left marks the opening price and one on the right marks the closing price. The length of these tics may be changed by bars. The symbol will be unchanged if the high and low prices are interchanged. See bars and `candlesticks`, and also the finance demo.

-- FSTEPS --

The `fsteps` style is only relevant to 2-d plotting. It connects consecutive points with two line segments: the first from (x1,y1) to (x1,y2) and the second from (x1,y2) to (x2,y2). See also steps demo.

-- HISTEPS --

The `histeps` style is only relevant to 2-d plotting. It is intended for plotting histograms. Y-values are assumed to be centered at the x-values; the point at x1 is represented as a horizontal line from ((x0+x1)/2,y1) to ((x1+x2)/2,y1). The lines representing the end points are extended so that the step is centered on at x. Adjacent points are connected by a vertical line at their average x, that is, from ((x1+x2)/2,y1) to ((x1+x2)/2,y2).

If autoscale is in effect, it selects the xrange from the data rather than the steps, so the end points will appear only half as wide as the others. See also steps demo.

`histeps` is only a plotting style; `gnuplot` does not have the ability to create bins and determine their population from some data set.

-- HISTOGRAMS --

The `histograms` style is only relevant to 2-d plotting. It produces a bar chart from a sequence of data columns in parallel. Each element of the `plot` command must specify a single input data source (e.g. one column of the input file), possibly with associated tic values or key titles. Four styles of histogram layout are currently supported.

 
      set style histogram clustered {gap <gapsize>}
      set style histogram errorbars {gap <gapsize>} {<linewidth>}
      set style histogram rowstacked
      set style histogram columnstacked

The default style corresponds to `set style histogram clustered gap 2`. In this style, each set of parallel data values is collected into a group of boxes clustered at the x-axis coordinate corresponding to their sequential position (row #) in the selected datafile columns. Thus if <n> datacolumns are selected, the first cluster is centered about x=1, and contains <n> boxes whose heights are taken from the first entry in the corresponding <n> data columns. This is followed by a gap and then a second cluster of boxes centered about x=2 corresponding to the second entry in the respective data columns, and so on. The default gap width of 2 indicates that the empty space between clusters is equivalent to the width of 2 boxes. All boxes derived from any one column are given the same fill color and/or pattern (see `set style fill`).

Each cluster of boxes is derived from a single row of the input data file. It is common in such input files that the first element of each row is a label. Labels from this column may be placed along the x-axis underneath the appropriate cluster of boxes with the `xticlabels` option to using.

The errorbars style is very similar to the `clustered` style, except that it requires two columns of input for each entry. The first column is treated as the height (y-value) of that box, exactly as for the `clustered` style. The second column is treated as an error magnitude, and used to generate a vertical error bar at the top of the box. The appearance of the error bar is controlled by the current value of bars and by the optional <linewidth> specification.

Two styles of stacked histogram are supported, chosen by the command `set style histogram {rowstacked|columnstacked}`. In these styles the data values from the selected columns are collected into stacks of boxes. The default stacking mode is `rowstacked`.

The `rowstacked` style places a box resting on the x-axis for each data value in the first selected column; the first data value results in a box a x=1, the second at x=2, and so on. Boxes corresponding to the second and subsequent data columns are layered on top of these, resulting in a stack of boxes at x=1 representing the first data value from each column, a stack of boxes at x=2 representing the second data value from each column, and so on. All boxes derived from any one column are given the same fill color and/or pattern (see `set style fill`).

The `columnstacked` style is similar, except that each stack of boxes is built up from a single data column. Each data value from the first specified column yields a box in the stack at x=1, each data value from the second specified column yields a box in the stack at x=2, and so on. In this style the color of each box is taken from the row number, rather than the column number, of the corresponding data field.

Box widths may be modified using the boxwidth command. Box fill styles may be set using the `set style fill` command.

Histograms always use the x1 axis, but may use either y1 or y2. If a plot contains both histograms and other plot styles, the non-histogram plot elements may use either the x1 or the x2 axis.

Examples:

To plot a data file containing multiple columns of data as a histogram of clustered boxes (the default style):

 
      set boxwidth 0.9 relative
      set style data histograms
      set style fill solid 1.0 border -1
      plot 'file.dat' using 2, '' using 4, '' using 6

This will produce a plot with clusters of three boxes (vertical bars) centered at each integral value on the x axis. If the first column of the input file contains labels, they may be placed along the x-axis using the variant command

 
      plot 'file.dat' using 2, '' using 4, '' using 6:xticlabels(1)

If the file contains both a magnitude and an error estimate for each value, then error bars can be added to the plot. The following commands will add error bars extending from (y-<error>) to (y+<error>), capped by horizontal bar ends drawn the same width as the box itself. The error bars and bar ends are drawn in black with linewidth 2.

 
      set bars fullwidth
      set style histogram errorbars gap 2 lt -1 lw 2
      plot 'file.dat' using 2:3, '' using 4:5, '' using 6:7:xticlabels(1)

To plot the same data as a rowstacked histogram:

 
      set style histogram rows
      plot 'file.dat' using 2, '' using 4, '' using 6:xtic(1)

This will produce a plot in which each vertical bar contains a stack of three segments, corresponding in height to the values found in columns 2, 4 and 6 of the datafile.

Finally, the commands

 
      set style histogram columnstacked
      plot 'file.dat' using 2, '' using 4, '' using 6

will produce three vertical stacks. The stack at x=1 will contain a box for each entry in column 2 of the datafile. The stack at x=2 will contain a box for each parallel entry in column 4 of the datafile, and the stack at x=3 a box for each entry of column 6. Because this interchanges gnuplot's usual interpretation of input rows and columns, the specification of key titles and x-axis tic labels must also be modified.

 
      set style histogram columnstacked
      plot '' u 5:key(1)            # uses first column to generate key titles
      plot '' u 5 title columnhead  # uses first row to generate xtic labels

-- NEWHISTOGRAM --

More than one set of histograms can appear in a single plot. In this case you can force a gap between them, and a separate label for each set, by using the plot command `newhistogram {"<title>"} {<linestyle>}`. For example

 
      set style histogram  cluster
      plot newhistogram "Set A", 'a' using 1, '' using 2, '' using 3, \
           newhistogram "Set B", 'b' using 1, '' using 2, '' using 3

The labels "Set A" and "Set B" will appear beneath the respective sets of histograms, under the overall x axis label.

The newhistogram command can also be used to force histogram coloring to begin with a specific color (linetype). By default colors will continue to increment successively even across histogram boundaries. Here is an example using the same coloring for multiple histograms

 
      plot newhistogram "Set A" lt 4, 'a' using 1, '' using 2, '' using 3, \
           newhistogram "Set B" lt 4, 'b' using 1, '' using 2, '' using 3

-- IMAGE --

The `image` style is intendend for plotting 2D images. It may be used for both `plot` and `splot` in the form of 3D data (x,y,value) or projected 4D data (x,y,z,value), respectively. It is assumed that in the viewing plane the image data forms an equidistant sampling grid in the viewing plane along two, not necessarily orthogonal, directions. In other words, groups of four adjacent points are assumed to form the same size parallelogram. The variable `value` in the tuples represent a palette color (gray value) for indexing in the current palette.

The `image` style will attempt to create a properly positioned and scaled data matrix to match the plot borders for those terminals supporting palettes and images. Such output is efficient and draws quickly. However, when a terminal driver does not support palettes and images, or when image support is not implemented, the `image` style reverts to drawing filled rectangular boxes for pixels, which is not as efficient. General parallelogram-shaped images currently always have filled parallelograms for pixels.

The coordinate of each data point of an image will lie at the center of a pixel. That is, an M x N set of data will form an image with M x N pixels. This is slightly different than pm3d elements where an M x N set of data will form a surface of (M-1) x (N-1) elements. The scan directions for the image data grid can be any of eight possible combinations.

Here are some specific comments about particular terminal drivers:

x11 and wxt - Pixels are either repeated or decimated to fit the display

 
      resolution; no other processing (filtering) is done.  Thus, aliasing may
      occur when decimating images having high spatial frequency content.

postscript (pslatex, epslatex, pstex) - Image is copied in its original

 
      resolution, and sample interpolation is turned off.

See also `rgbimage`.

-- IMPULSES --

The `impulses` style displays a vertical line from the x axis (not the graph border), or from the grid base for `splot`, to each point.

-- LABELS --

The `labels` style is available only if gnuplot is built with configuration option -enable-datastrings. For a 2-D plot with labels you must specify 3 input data columns; the text string found in the third column is printed at the X and Y coordinates generated by the first two column specifiers. The font, color, rotation angle and other properties of the printed text may be specified as additional command options (see label). The example below will generate a 2-D plot with text labels taken from column 4 of the input file (`tc lt 2` is shorthand for `textcolor linetype 2`, which is green).

 
  plot 'datafile' using 1:(0.5 * $2):4 with labels font "arial,11" tc lt 2

The `labels` style can also be used in 3-D plots. In this case four input column specifiers are required, corresponding to X Y Z and text.

 
  splot 'datafile' using 1:2:3:4 with labels

See also `datastrings`, `set style data`.

-- LINES --

The `lines` style connects adjacent points with straight line segments. See also `linetype`, `linewidth`, and `linestyle`.

-- LINESPOINTS --

The `linespoints` style does both `lines` and `points`, that is, it draws a small symbol at each point and then connects adjacent points with straight line segments. The command pointsize may be used to change the size of the points. See pointsize for its usage.

`linespoints` may be abbreviated `lp`.

-- POINTS --

The `points` style displays a small symbol at each point. The command pointsize may be used to change the size of the points. See pointsize for its usage.

-- STEPS --

The `steps` style is only relevant to 2-d plotting. It connects consecutive points with two line segments: the first from (x1,y1) to (x2,y1) and the second from (x2,y1) to (x2,y2). See also steps demo.

-- RGBIMAGE --

The `rgbimage` style is intended for plotting 2D images and is similar in concept to `image`. See `image` for details. The difference is that 5D data (x,y,r,g,b) for `plot` and 6D data (x,y,z,r,g,b) for `splot` describe the coordinates and color components of an image.

See also `image`.

-- VECTORS --

The 2D `vectors` style draws a vector from (x,y) to (x+xdelta,y+ydelta). Thus it requires four columns of data. It also draws a small arrowhead at the end of the vector. The 3D `vectors` style is similar, but requires six columns of data. splot with vectors is supported only for `set mapping cartesian`. The keywords "with vectors" may be followed by arrow style specifications. See `arrowstyle` for more details.

Example:

 
      plot 'file.dat' using 1:2:3:4 with vectors head filled lt 2
      splot 'file.dat' using 1:2:3:(1):(1):(1) with vectors filled head lw 2

`set clip one` and `set clip two` affect vectors drawn in 2D. Please see clip and `arrowstyle`.

-- XERRORBARS --

The `xerrorbars` style is only relevant to 2-d data plots. `xerrorbars` is like `dots`, except that a horizontal error bar is also drawn. At each point (x,y), a line is drawn from (xlow,y) to (xhigh,y) or from (x-xdelta,y) to (x+xdelta,y), depending on how many data columns are provided. A tic mark is placed at the ends of the error bar (unless bars is used--see bars for details).

-- XYERRORBARS --

The `xyerrorbars` style is only relevant to 2-d data plots. `xyerrorbars` is like `dots`, except that horizontal and vertical error bars are also drawn. At each point (x,y), lines are drawn from (x,y-ydelta) to (x,y+ydelta) and from (x-xdelta,y) to (x+xdelta,y) or from (x,ylow) to (x,yhigh) and from (xlow,y) to (xhigh,y), depending upon the number of data columns provided. A tic mark is placed at the ends of the error bar (unless bars is used--see bars for details).

If data are provided in an unsupported mixed form, the using filter on the `plot` command should be used to set up the appropriate form. For example, if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use

 
      plot 'data' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars

-- YERRORBARS --

The `yerrorbars` (or errorbars) style is only relevant to 2-d data plots. `yerrorbars` is like `points`, except that a vertical error bar is also drawn. At each point (x,y), a line is drawn from (x,y-ydelta) to (x,y+ydelta) or from (x,ylow) to (x,yhigh), depending on how many data columns are provided. A tic mark is placed at the ends of the error bar (unless bars is used--see bars for details). See also errorbar demo.

-- XERRORLINES --

The `xerrorlines` style is only relevant to 2-d data plots. `xerrorlines` is like `linespoints`, except that a horizontal error line is also drawn. At each point (x,y), a line is drawn from (xlow,y) to (xhigh,y) or from (x-xdelta,y) to (x+xdelta,y), depending on how many data columns are provided. A tic mark is placed at the ends of the error bar (unless bars is used--see bars for details).

-- XYERRORLINES --

The `xyerrorlines` style is only relevant to 2-d data plots. `xyerrorlines` is like `linespoints`, except that horizontal and vertical error bars are also drawn. At each point (x,y), lines are drawn from (x,y-ydelta) to (x,y+ydelta) and from (x-xdelta,y) to (x+xdelta,y) or from (x,ylow) to (x,yhigh) and from (xlow,y) to (xhigh,y), depending upon the number of data columns provided. A tic mark is placed at the ends of the error bar (unless bars is used--see bars for details).

If data are provided in an unsupported mixed form, the using filter on the `plot` command should be used to set up the appropriate form. For example, if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use

 
      plot 'data' using 1:2:($1-$3):($1+$3):4:5 with xyerrorlines

-- YERRORLINES --

The `yerrorlines` (or errorlines) style is only relevant to 2-d data plots. `yerrorlines` is like `linespoints`, except that a vertical error line is also drawn. At each point (x,y), a line is drawn from (x,y-ydelta) to (x,y+ydelta) or from (x,ylow) to (x,yhigh), depending on how many data columns are provided. A tic mark is placed at the ends of the error bar (unless bars is used--see bars for details). See also errorbar demo.


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2.21.60 surface

The command surface controls the display of surfaces by `splot`.

Syntax:

 
      set surface
      unset surface
      show surface

The surface is drawn with the style specified by with, or else the appropriate style, data or function.

Whenever surface is issued, `splot` will not draw points or lines corresponding to the function or data file points. Contours may still be drawn on the surface, depending on the contour option. `unset surface; set contour base` is useful for displaying contours on the grid base. See also contour.


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2.21.61 table

When table mode is enabled, `plot` and `splot` commands print out a multicolumn ASCII table of X Y {Z} R values rather than creating an actual plot on the current terminal. The character R takes on one of three values: "i" if the point is in the active range, "o" if it is out-of-range, or "u" if it is undefined. The data format is determined by the format of the axis labels (see `set format`), and the columns are separated by single spaces. This can be useful if you want to generate contours and then save them for further use, perhaps for plotting with `plot`; see contour for example. The same method can be used to save interpolated data (see samples and dgrid3d).

Syntax:

 
      set table {"outfile"}
      plot <whatever>
      unset table

Tabular output is written to the named file, if any, otherwise it is written to the current value of output. You must explicitly table in order to go back to normal plotting on the current terminal.


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2.21.62 terminal

`gnuplot` supports many different graphics devices. Use `set terminal` to tell `gnuplot` what kind of output to generate. Use output to redirect that output to a file or device.

Syntax:

 
      set terminal {<terminal-type> | push | pop}
      show terminal

If <terminal-type> is omitted, `gnuplot` will list the available terminal types. <terminal-type> may be abbreviated.

If both `set terminal` and output are used together, it is safest to give `set terminal` first, because some terminals set a flag which is needed in some operating systems.

Several terminals have many additional options. For example, see `png`, or postscript. The options used by a previous invocation `set term <term> <options>` of a given `<term>` are remembered, thus subsequent `set term <term>` does not reset them. This helps in printing, for instance, when switching among different terminals--previous options don't have to be repeated.

The command `set term push` remembers the current terminal including its settings while `set term pop` restores it. This is equivalent to `save term` and `load term`, but without accessing the filesystem. Therefore they can be used to achieve platform independent restoring of the terminal after printing, for instance. After gnuplot's startup, the default terminal or that from `startup` file is pushed automatically. Therefore portable scripts can rely that `set term pop` restores the default terminal on a given platform unless another terminal has been pushed explicitly.

For a complete list of available terminal types, see `terminal`.


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2.21.63 termoption

The termoption command allows you to change the behaviour of the current terminal without requiring a new `set terminal` command. Only one option can be changed per command, and only a small number of options can be changed this way. Currently the only options accepted are

 
     set termoption {no}enhanced
     set termoption font "<fontname>{,<fontsize>}"


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2.21.64 tics

Control of the major (labelled) tics on all axes at once is possible with the `set tics` command.

Fine control of the major (labelled) tics on all axes at once is possible with the `set tics` command. The tics may be turned off with the `unset tics` command, and may be turned on (the default state) with `set tics`. Similar commands (by preceding 'tics' by the axis name) control the major tics on a single axis.

Syntax:

 
      set tics {axis | border} {{no}mirror}
               {in | out} {scale {default | <major> {,<minor>}}}
               {{no}rotate {by <ang>}} {offset <offset> | nooffset}
               { font "name{,<size>}" }
               { textcolor <colorspec> }
      unset tics
      show tics

All specified options apply to all axes, i.e., x, y, z, x2, y2, and cb.

`axis` or border tells `gnuplot` to put the tics (both the tics themselves and the accompanying labels) along the axis or the border, respectively. If the axis is very close to the border, the `axis` option will move the tic labels to outside the border in case the border is printed (see border). The relevant margin settings will usually be sized badly by the automatic layout algorithm in this case.

`mirror` tells `gnuplot` to put unlabelled tics at the same positions on the opposite border. `nomirror` does what you think it does.

`in` and `out` change the tic marks to be drawn inwards or outwards.

With `scale`, the size of the tic marks can be adjusted. If <minor> is not specified, it is 0.5*<major>. The default size 1.0 for major tics and 0.5 for minor tics is requested by `scale default`.

`rotate` asks `gnuplot` to rotate the text through 90 degrees, which will be done if the terminal driver in use supports text rotation. `norotate` cancels this. `rotate by <ang>` asks for rotation by <ang> degrees, supported by some terminal types.

The defaults are `border mirror norotate` for tics on the x and y axes, and `border nomirror norotate` for tics on the x2 and y2 axes. For the z axis, the default is `nomirror`.

The <offset> is specified by either x,y or x,y,z, and may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. <offset> is the offset of the tics texts from their default positions, while the default coordinate system is `character`. See `coordinates` for details. `nooffset` switches off the offset.

`set tics` with no options restores to place tics inwards. Every other options are retained.

See also xtics for more control of major (labelled) tic marks and mxtics for control of minor tic marks. These commands provide control at a axis by axis basis.


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2.21.65 ticslevel

See xyplane.


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2.21.66 ticscale

The ticscale command is deprecated, use `set tics scale` instead.


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2.21.67 timestamp

The command timestamp places the time and date of the plot in the left margin.

Syntax:

 
      set timestamp {"<format>"} {top|bottom} {{no}rotate}
                    {offset {<xoff>}{,<yoff>}} {font "<fontspec>"}
      unset timestamp
      show timestamp

The format string allows you to choose the format used to write the date and time. Its default value is what asctime() uses: "%a %b %d %H:%M:%S %Y" (weekday, month name, day of the month, hours, minutes, seconds, four-digit year). With `top` or `bottom` you can place the timestamp at the top or bottom of the left margin (default: bottom). `rotate` lets you write the timestamp vertically, if your terminal supports vertical text. The constants <xoff> and <yoff> are offsets that let you adjust the position more finely. <font> is used to specify the font with which the time is to be written.

The abbreviation `time` may be used in place of timestamp.

Example:

 
      set timestamp "%d/%m/%y %H:%M" offset 80,-2 font "Helvetica"

See timefmt for more information about time format strings.


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2.21.68 timefmt

This command applies to timeseries where data are composed of dates/times. It has no meaning unless the command `set xdata time` is given also.

Syntax:

 
      set timefmt "<format string>"
      show timefmt

The string argument tells `gnuplot` how to read timedata from the datafile. The valid formats are:

 
      Format       Explanation
      %d           day of the month, 1--31
      %m           month of the year, 1--12
      %y           year, 0--99
      %Y           year, 4-digit
      %j           day of the year, 1--365
      %H           hour, 0--24
      %M           minute, 0--60
      %s           seconds since the Unix epoch (1970-01-01, 00:00 UTC)
      %S           second, 0--60
      %b           three-character abbreviation of the name of the month
      %B           name of the month

Any character is allowed in the string, but must match exactly. \t (tab) is recognized. Backslash-octals (\nnn) are converted to char. If there is no separating character between the time/date elements, then %d, %m, %y, %H, %M and %S read two digits each, %Y reads four digits and %j reads three digits. %b requires three characters, and %B requires as many as it needs.

Spaces are treated slightly differently. A space in the string stands for zero or more whitespace characters in the file. That is, "%H %M" can be used to read "1220" and "12 20" as well as "12 20".

Each set of non-blank characters in the timedata counts as one column in the `using n:n` specification. Thus `11:11 25/12/76 21.0` consists of three columns. To avoid confusion, `gnuplot` requires that you provide a complete using specification if your file contains timedata.

Since `gnuplot` cannot read non-numerical text, if the date format includes the day or month in words, the format string must exclude this text. But it can still be printed with the "%a", "%A", "%b", or "%B" specifier: see `set format` for more details about these and other options for printing timedata. (`gnuplot` will determine the proper month and weekday from the numerical values.)

See also xdata and `Time/date` for more information.

Example:

 
      set timefmt "%d/%m/%Y\t%H:%M"

tells `gnuplot` to read date and time separated by tab. (But look closely at your data--what began as a tab may have been converted to spaces somewhere along the line; the format string must match what is actually in the file.) See also time data demo.


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2.21.69 title

The `set title` command produces a plot title that is centered at the top of the plot. `set title` is a special case of label.

Syntax:

 
      set title {"<title-text>"} {offset <offset>} {font "<font>{,<size>}"}
                {{textcolor | tc} {<colorspec> | default}} {{no}enhanced}
      show title

If <offset> is specified by either x,y or x,y,z the title is moved by the given offset. It may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. See `coordinates` for details. By default, the `character` coordinate system is used. For example, "`set title offset 0,-1`" will change only the y offset of the title, moving the title down by roughly the height of one character. The size of a character depends on both the font and the terminal.

<font> is used to specify the font with which the title is to be written; the units of the font <size> depend upon which terminal is used.

`textcolor <colorspec>` changes the color of the text. <colorspec> can be a linetype, an rgb color, or a palette mapping. See help for colorspec and palette.

`noenhanced` requests that the title not be processed by the enhanced text mode parser, even if enhanced text mode is currently active.

`set title` with no parameters clears the title.

See `syntax` for details about the processing of backslash sequences and the distinction between single- and double-quotes.


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2.21.70 tmargin

The command tmargin sets the size of the top margin. Please see margin for details.


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2.21.71 trange

The trange command sets the parametric range used to compute x and y values when in parametric or polar modes. Please see xrange for details.


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2.21.72 urange

The urange and vrange commands set the parametric ranges used to compute x, y, and z values when in `splot` parametric mode. Please see xrange for details.


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2.21.73 variables

The variables command lists all user-defined variables and their values.

Syntax:

 
      show variables {all}

With the optional keyword "all", also the variables that begin with `GPVAL_` are listed.


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2.21.74 version

The version command lists the version of gnuplot being run, its last modification date, the copyright holders, and email addresses for the FAQ, the gnuplot-info mailing list, and reporting bugs-in short, the information listed on the screen when the program is invoked interactively.

Syntax:

 
      show version {long}

When the `long` option is given, it also lists the operating system, the compilation options used when `gnuplot` was installed, the location of the help file, and (again) the useful email addresses.


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2.21.75 view

The view command sets the viewing angle for `splot`s. It controls how the 3-d coordinates of the plot are mapped into the 2-d screen space. It provides controls for both rotation and scaling of the plotted data, but supports orthographic projections only. It supports both 3D projection or orthogonal 2D projection into a 2D plot-like map.

Syntax:

 
      set view { <rot_x>{,{<rot_z>}{,{<scale>}{,<scale_z>}}} | map }
      show view

where <rot_x> and <rot_z> control the rotation angles (in degrees) in a virtual 3-d coordinate system aligned with the screen such that initially (that is, before the rotations are performed) the screen horizontal axis is x, screen vertical axis is y, and the axis perpendicular to the screen is z. The first rotation applied is <rot_x> around the x axis. The second rotation applied is <rot_z> around the new z axis.

Command `set view map` is used to represent the drawing as a map. It can be used for contour plots, or for color pm3d maps. In the latter, take care that you properly use zrange and cbrange for input data point filtering and color range scaling, respectively.

<rot_x> is bounded to the [0:180] range with a default of 60 degrees, while <rot_z> is bounded to the [0:360] range with a default of 30 degrees. <scale> controls the scaling of the entire `splot`, while <scale_z> scales the z axis only. Both scales default to 1.0.

Examples:

 
      set view 60, 30, 1, 1
      set view ,,0.5

The first sets all the four default values. The second changes only scale, to 0.5.

See also ticslevel.


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2.21.76 vrange

The urange and vrange commands set the parametric ranges used to compute x, y, and z values when in `splot` parametric mode. Please see xrange for details.


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2.21.77 x2data

The x2data command sets data on the x2 (top) axis to timeseries (dates/times). Please see xdata.


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2.21.78 x2dtics

The x2dtics command changes tics on the x2 (top) axis to days of the week. Please see xdtics for details.


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2.21.79 x2label

The x2label command sets the label for the x2 (top) axis. Please see xlabel.


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2.21.80 x2mtics

The x2mtics command changes tics on the x2 (top) axis to months of the year. Please see xmtics for details.


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2.21.81 x2range

The x2range command sets the horizontal range that will be displayed on the x2 (top) axis. Please see xrange for details.


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2.21.82 x2tics

The x2tics command controls major (labelled) tics on the x2 (top) axis. Please see xtics for details.


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2.21.83 x2zeroaxis

The x2zeroaxis command draws a line at the origin of the x2 (top) axis (y2 = 0). For details, please see zeroaxis.


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2.21.84 xdata

This command sets the datatype on the x axis to time/date. A similar command does the same thing for each of the other axes.

Syntax:

 
      set xdata {time}
      show xdata

The same syntax applies to ydata, zdata, x2data, y2data and cbdata.

The `time` option signals that the datatype is indeed time/date. If the option is not specified, the datatype reverts to normal.

See timefmt to tell gnuplot how to read date or time data. The time/date is converted to seconds from start of the century. There is currently only one timefmt, which implies that all the time/date columns must conform to this format. Specification of ranges should be supplied as quoted strings according to this format to avoid interpretation of the time/date as an expression.

The function 'strftime' (type "man strftime" on unix to look it up) is used to print tic-mark labels. `gnuplot` tries to figure out a reasonable format for this unless the `set format x "string"` has supplied something that does not look like a decimal format (more than one '%' or neither %f nor %g).

See also `Time/date` for more information.


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2.21.85 xdtics

The xdtics commands converts the x-axis tic marks to days of the week where 0=Sun and 6=Sat. Overflows are converted modulo 7 to dates. `set noxdtics` returns the labels to their default values. Similar commands do the same things for the other axes.

Syntax:

 
      set xdtics
      unset xdtics
      show xdtics

The same syntax applies to ydtics, zdtics, x2dtics, y2dtics and cbdtics.

See also the `set format` command.


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2.21.86 xlabel

The xlabel command sets the x axis label. Similar commands set labels on the other axes.

Syntax:

 
      set xlabel {"<label>"} {offset <offset>} {font "<font>{,<size>}"}
                 {{textcolor | tc} {lt <line_type> | default}} {{no}enhanced}
                 {rotate by <degrees>}
      show xlabel

The same syntax applies to x2label, ylabel, y2label, zlabel and cblabel.

If <offset> is specified by either x,y or x,y,z the label is moved by the given offset. It may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. See `coordinates` for details. By default, the `character` coordinate system is used. For example, "`set xlabel offset -1,0`" will change only the x offset of the title, moving the label roughly one character width to the left. The size of a character depends on both the font and the terminal.

<font> is used to specify the font in which the label is written; the units of the font <size> depend upon which terminal is used.

`textcolor lt <n>` sets the text color to that of line type <n>.

`noenhanced` requests that the label text not be processed by the enhanced text mode parser, even if enhanced text mode is currently active.

To clear a label, put no options on the command line, e.g., "y2label".

The default positions of the axis labels are as follows:

xlabel: The x-axis label is centered below the bottom axis.

ylabel: The position of the y-axis label depends on the terminal, and can be one of the following three positions:

1. Horizontal text flushed left at the top left of the plot. Terminals that cannot rotate text will probably use this method. If x2tics is also in use, the ylabel may overwrite the left-most x2tic label. This may be remedied by adjusting the ylabel position or the left margin.

2. Vertical text centered vertically at the left of the plot. Terminals that can rotate text will probably use this method.

3. Horizontal text centered vertically at the left of the plot. The EEPIC, LaTeX and TPIC drivers use this method. The EEPIC driver will produce a stack of characters so as not to overwrite the plot. With other drivers (such as LaTeX and TPIC), the user probably has to insert line breaks using \\ to prevent the ylabel from overwriting the plot.

zlabel: The z-axis label is centered along the z axis and placed in the space above the grid level.

cblabel: The color box axis label is centered along the box and placed below or right according to horizontal or vertical color box gradient.

y2label: The y2-axis label is placed to the right of the y2 axis. The position is terminal-dependent in the same manner as is the y-axis label.

x2label: The x2-axis label is placed above the top axis but below the plot title. It is also possible to create an x2-axis label by using new-line characters to make a multi-line plot title, e.g.,

 
      set title "This is the title\n\nThis is the x2label"

Note that double quotes must be used. The same font will be used for both lines, of course.

The y and y2 axis labels can be explicitly rotated from their default orientation, but this applies only to 2D plots and only on terminals that support text rotation.

If you are not satisfied with the default position of an axis label, use label instead-that command gives you much more control over where text is placed.

Please see `syntax` for further information about backslash processing and the difference between single- and double-quoted strings.


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2.21.87 xmtics

The xmtics command converts the x-axis tic marks to months of the year where 1=Jan and 12=Dec. Overflows are converted modulo 12 to months. The tics are returned to their default labels by xmtics. Similar commands perform the same duties for the other axes.

Syntax:

 
      set xmtics
      unset xmtics
      show xmtics

The same syntax applies to x2mtics, ymtics, y2mtics, zmtics and cbmtics.

See also the `set format` command.


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2.21.88 xrange

The xrange command sets the horizontal range that will be displayed. A similar command exists for each of the other axes, as well as for the polar radius r and the parametric variables t, u, and v.

Syntax:

 
      set xrange { [{{<min>}:{<max>}}] {{no}reverse} {{no}writeback} }
                 | restore
      show xrange

where <min> and <max> terms are constants, expressions or an asterisk to set autoscaling. If the data are time/date, you must give the range as a quoted string according to the timefmt format. Any value omitted will not be changed.

The same syntax applies to yrange, zrange, x2range, y2range, cbrange, rrange, trange, urange and vrange.

The `reverse` option reverses the direction of the axis, e.g., `set xrange [0:1] reverse` will produce an axis with 1 on the left and 0 on the right. This is identical to the axis produced by `set xrange [1:0]`, of course. `reverse` is intended primarily for use with autoscale.

The `writeback` option essentially saves the range found by autoscale in the buffers that would be filled by xrange. This is useful if you wish to plot several functions together but have the range determined by only some of them. The `writeback` operation is performed during the `plot` execution, so it must be specified before that command. To restore, the last saved horizontal range use `set xrange restore`. For example,

 
      set xrange [-10:10]
      set yrange [] writeback
      plot sin(x)
      set yrange restore
      replot x/2

results in a yrange of [-1:1] as found only from the range of sin(x); the [-5:5] range of x/2 is ignored. Executing yrange after each command in the above example should help you understand what is going on.

In 2-d, xrange and yrange determine the extent of the axes, trange determines the range of the parametric variable in parametric mode or the range of the angle in polar mode. Similarly in parametric 3-d, xrange, yrange, and zrange govern the axes and urange and vrange govern the parametric variables.

In polar mode, rrange determines the radial range plotted. <rmin> acts as an additive constant to the radius, whereas <rmax> acts as a clip to the radius--no point with radius greater than <rmax> will be plotted. xrange and yrange are affected--the ranges can be set as if the graph was of r(t)-rmin, with rmin added to all the labels.

Any range may be partially or totally autoscaled, although it may not make sense to autoscale a parametric variable unless it is plotted with data.

Ranges may also be specified on the `plot` command line. A range given on the plot line will be used for that single `plot` command; a range given by a `set` command will be used for all subsequent plots that do not specify their own ranges. The same holds true for `splot`.

Examples:

To set the xrange to the default:

 
      set xrange [-10:10]

To set the yrange to increase downwards:

 
      set yrange [10:-10]

To change zmax to 10 without affecting zmin (which may still be autoscaled):

 
      set zrange [:10]

To autoscale xmin while leaving xmax unchanged:

 
      set xrange [*:]


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2.21.89 xtics

Fine control of the major (labelled) tics on the x axis is possible with the xtics command. The tics may be turned off with the xtics command, and may be turned on (the default state) with xtics. Similar commands control the major tics on the y, z, x2 and y2 axes.

Syntax:

 
      set xtics {axis | border} {{no}mirror}
                {in | out} {scale {default | <major> {,<minor>}}}
                {{no}rotate {by <ang>}} {offset <offset> | nooffset}
                {add}
                {  autofreq
                 | <incr>
                 | <start>, <incr> {,<end>}
                 | ({"<label>"} <pos> {<level>} {,{"<label>"}...) }
                { font "name{,<size>}" }
                { textcolor <colorspec> }
      unset xtics
      show xtics

The same syntax applies to ytics, ztics, x2tics, y2tics and cbtics.

`axis` or border tells `gnuplot` to put the tics (both the tics themselves and the accompanying labels) along the axis or the border, respectively. If the axis is very close to the border, the `axis` option will move the tic labels to outside the border. The relevant margin settings will usually be sized badly by the automatic layout algorithm in this case.

`mirror` tells `gnuplot` to put unlabelled tics at the same positions on the opposite border. `nomirror` does what you think it does.

`in` and `out` change the tic marks to be drawn inwards or outwards.

With `scale`, the size of the tic marks can be adjusted. If <minor> is not specified, it is 0.5*<major>. The default size 1.0 for major tics and 0.5 for minor tics is requested by `scale default`.

`rotate` asks `gnuplot` to rotate the text through 90 degrees, which will be done if the terminal driver in use supports text rotation. `norotate` cancels this. `rotate by <ang>` asks for rotation by <ang> degrees, supported by some terminal types.

The defaults are `border mirror norotate` for tics on the x and y axes, and `border nomirror norotate` for tics on the x2 and y2 axes. For the z axis, the `{axis | border}` option is not available and the default is `nomirror`. If you do want to mirror the z-axis tics, you might want to create a bit more room for them with border.

The <offset> is specified by either x,y or x,y,z, and may be preceded by `first`, `second`, `graph`, `screen`, or `character` to select the coordinate system. <offset> is the offset of the tics texts from their default positions, while the default coordinate system is `character`. See `coordinates` for details. `nooffset` switches off the offset.

Example:

Move xtics more closely to the plot.

 
      set xtics offset 0,graph 0.05

xtics with no options restores the default border or axis if xtics are being displayed; otherwise it has no effect. Any previously specified tic frequency or position {and labels} are retained.

Positions of the tics are calculated automatically by default or if the `autofreq` option is given; otherwise they may be specified in either of two forms:

The implicit <start>, <incr>, <end> form specifies that a series of tics will be plotted on the axis between the values <start> and <end> with an increment of <incr>. If <end> is not given, it is assumed to be infinity. The increment may be negative. If neither <start> nor <end> is given, <start> is assumed to be negative infinity, <end> is assumed to be positive infinity, and the tics will be drawn at integral multiples of <incr>. If the axis is logarithmic, the increment will be used as a multiplicative factor.

If you specify to a negative <start> or <incr> after a numerical value (e.g., `rotate by <angle>` or `offset <offset>`), the parser fails because it subtracts <start> or <incr> from that value. As a workaround, specify `0-<start>` resp. `0-<incr>` in that case.

Example:

 
      set xtics border offset 0,0.5 -5,1,5

Fails with 'invalid expression' at the last comma.

 
      set xtics border offset 0,0.5 0-5,1,5

or

 
      set xtics offset 0,0.5 border -5,1,5

Sets tics at the border, tics text with an offset of 0,0.5 characters, and sets the start, increment, and end to -5, 1, and 5, as requested.

The `set grid` options 'front', 'back' and 'layerdefault' affect the drawing order of the xtics, too.

Examples:

Make tics at 0, 0.5, 1, 1.5, ..., 9.5, 10.

 
      set xtics 0,.5,10

Make tics at ..., -10, -5, 0, 5, 10, ...

 
      set xtics 5

Make tics at 1, 100, 1e4, 1e6, 1e8.

 
      set logscale x; set xtics 1,100,1e8

The explicit ("<label>" <pos> <level>, ...) form allows arbitrary tic positions or non-numeric tic labels. In this form, the tics do not need to be listed in numerical order. Each tic has a position, optionally with a label. Note that the label is a string enclosed by quotes. It may be a constant string, such as "hello", may contain formatting information for converting the position into its label, such as "%3f clients", or may be empty, "". See `set format` for more information. If no string is given, the default label (numerical) is used.

An explicit tic mark has a third parameter, the "level". The default is level 0, a major tic. A level of 1 generates a minor tic. If the level is specified, then the label must also be supplied.

Examples:

 
      set xtics ("low" 0, "medium" 50, "high" 100)
      set xtics (1,2,4,8,16,32,64,128,256,512,1024)
      set ytics ("bottom" 0, "" 10, "top" 20)
      set ytics ("bottom" 0, "" 10 1, "top" 20)

In the second example, all tics are labelled. In the third, only the end tics are labelled. In the fourth, the unlabeled tic is a minor tic.

Normally if explicit tics are given, they are used instead of auto-generated tics. Conversely if you specify `set xtics auto` or the like it will erase any previously specified explicit tics. You can mix explicit and auto- generated tics by using the keyword `add`, which must appear before the tic style being added.

Example:

 
      set xtics 0,.5,10
      set xtics add ("Pi" 3.14159)

This will automatically generate tic marks every 0.5 along x, but will also add an explicit labeled tic mark at pi.

However they are specified, tics will only be plotted when in range.

Format (or omission) of the tic labels is controlled by `set format`, unless the explicit text of a label is included in the `set xtics ("<label>")` form.

Minor (unlabelled) tics can be added automatically by the mxtics command, or at explicit positions by the `set xtics ("" <pos> 1, ...)` form.

In case of timeseries data, position values must be given as quoted dates or times according to the format timefmt. If the <start>, <incr>, <end> form is used, <start> and <end> must be given according to timefmt, but <incr> must be in seconds. Times will be written out according to the format given on `set format`, however.

Examples:

 
      set xdata time
      set timefmt "%d/%m"
      set format x "%b %d"
      set xrange ["01/12":"06/12"]
      set xtics "01/12", 172800, "05/12"

 
      set xdata time
      set timefmt "%d/%m"
      set format x "%b %d"
      set xrange ["01/12":"06/12"]
      set xtics ("01/12", "" "03/12", "05/12")

Both of these will produce tics "Dec 1", "Dec 3", and "Dec 5", but in the second example the tic at "Dec 3" will be unlabelled.


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2.21.90 xyplane

The xyplane command adjusts the position at which the xy plane is drawn in a 3D plot. The synonym "set ticslevel" is accepted for backwards compatibility.

Syntax:

 
      set ticslevel <frac>
      set xyplane <frac>
      set xyplane at <zvalue>
      show xyplane

The form `set ticslevel <frac>` places the xy plane below the range in Z, where the distance from the xy plane to Zmin is given as a fraction of the total range in z. The default value is 0.5. Negative values are permitted, but tic labels on the three axes may overlap.

To place the xy-plane at a position 'pos' on the z-axis, ticslevel may be set equal to (pos - zmin) / (zmin - zmax). However, this position will change if the z range is changed.

The alternative form `set xyplane at <zvalue>` fixes the placement of the xy plane at a specific Z value regardless of the current z range. Thus to force the x, y, and z axes to meet at a common origin one would specify `set xyplane at 0`.

See also view, and zeroaxis.


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2.21.91 xzeroaxis

The xzeroaxis command draws a line at y = 0. For details, please see zeroaxis.


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2.21.92 y2data

The y2data command sets y2 (right-hand) axis data to timeseries (dates/times). Please see xdata.


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2.21.93 y2dtics

The y2dtics command changes tics on the y2 (right-hand) axis to days of the week. Please see xdtics for details.


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2.21.94 y2label

The y2label command sets the label for the y2 (right-hand) axis. Please see xlabel.


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2.21.95 y2mtics

The y2mtics command changes tics on the y2 (right-hand) axis to months of the year. Please see xmtics for details.


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2.21.96 y2range

The y2range command sets the vertical range that will be displayed on the y2 (right-hand) axis. Please see xrange for details.


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2.21.97 y2tics

The y2tics command controls major (labelled) tics on the y2 (right-hand) axis. Please see xtics for details.


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2.21.98 y2zeroaxis

The y2zeroaxis command draws a line at the origin of the y2 (right-hand) axis (x2 = 0). For details, please see zeroaxis.


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2.21.99 ydata

The ydata commands sets y-axis data to timeseries (dates/times). Please see xdata.


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2.21.100 ydtics

The ydtics command changes tics on the y axis to days of the week. Please see xdtics for details.


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2.21.101 ylabel

This command sets the label for the y axis. Please see xlabel.


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2.21.102 ymtics

The ymtics command changes tics on the y axis to months of the year. Please see xmtics for details.


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2.21.103 yrange

The yrange command sets the vertical range that will be displayed on the y axis. Please see xrange for details.


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2.21.104 ytics

The ytics command controls major (labelled) tics on the y axis. Please see xtics for details.


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2.21.105 yzeroaxis

The yzeroaxis command draws a line at x = 0. For details, please see zeroaxis.


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2.21.106 zdata

The zdata command sets zaxis data to timeseries (dates/times). Please see xdata.


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2.21.107 zdtics

The zdtics command changes tics on the z axis to days of the week. Please see xdtics for details.


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2.21.108 zzeroaxis

The zzeroaxis command draws a line through (x=0,y=0). This has no effect on 2D plots, including splot with `set view map`. For details, please see zeroaxis and xyplane.


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2.21.109 cbdata

Set color box axis data to timeseries (dates/times). Please see xdata.


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2.21.110 cbdtics

The cbdtics command changes tics on the color box axis to days of the week. Please see xdtics for details.


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2.21.111 zero

The `zero` value is the default threshold for values approaching 0.0.

Syntax:

 
      set zero <expression>
      show zero

`gnuplot` will not plot a point if its imaginary part is greater in magnitude than the `zero` threshold. This threshold is also used in various other parts of `gnuplot` as a (crude) numerical-error threshold. The default `zero` value is 1e-8. `zero` values larger than 1e-3 (the reciprocal of the number of pixels in a typical bitmap display) should probably be avoided, but it is not unreasonable to set `zero` to 0.0.


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2.21.112 zeroaxis

The x axis may be drawn by xzeroaxis and removed by xzeroaxis. Similar commands behave similarly for the y, x2, y2, and z axes.

Syntax:

 
      set {x|x2|y|y2|z}zeroaxis { {linestyle | ls <line_style>}
                                 | { linetype | lt <line_type>}
                                   { linewidth | lw <line_width>}}
      unset {x|x2|y|y2|z}zeroaxis
      show {x|y|z}zeroaxis

By default, these options are off. The selected zero axis is drawn with a line of type <line_type> and width <line_width> (if supported by the terminal driver currently in use), or a user-defined style <line_style>.

If no linetype is specified, any zero axes selected will be drawn using the axis linetype (linetype 0).

zeroaxis is equivalent to yzeroaxis. Note that the z-axis must be set separately using zzeroaxis.

Examples:

To simply have the y=0 axis drawn visibly:

 
       set xzeroaxis

If you want a thick line in a different color or pattern, instead:

 
       set xzeroaxis linetype 3 linewidth 2.5


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2.21.113 zlabel

This command sets the label for the z axis. Please see xlabel.


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2.21.114 zmtics

The zmtics command changes tics on the z axis to months of the year. Please see xmtics for details.


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2.21.115 zrange

The zrange command sets the range that will be displayed on the z axis. The zrange is used only by `splot` and is ignored by `plot`. Please see xrange for details.


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2.21.116 ztics

The ztics command controls major (labelled) tics on the z axis. Please see xtics for details.


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2.21.117 cblabel

This command sets the label for the color box axis. Please see xlabel.


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2.21.118 cbmtics

The cbmtics command changes tics on the color box axis to months of the year. Please see xmtics for details.


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2.21.119 cbrange

The cbrange command sets the range of values which are colored using the current palette by styles pm3d, `with image` and palette. Values outside of the color range use color of the nearest extreme.

If the cb-axis is autoscaled in `splot`, then the colorbox range is taken from zrange. Points drawn in `splot ... pm3d|palette` can be filtered by using different zrange and cbrange.

Please see xrange for details on cbrange syntax. See also palette and `set colorbox`.


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2.21.120 cbtics

The cbtics command controls major (labelled) tics on the color box axis. Please see xtics for details.


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2.22 shell

The shell command spawns an interactive shell. To return to `gnuplot`, type `logout` if using VMS, exit or the END-OF-FILE character if using Unix, `endcli` if using AmigaOS, or exit if using MS-DOS or OS/2.

There are two ways of spawning a shell command: using `system` command or via `!` ($ if using VMS). The former command takes a string as a parameter and thus it can be used anywhere among other gnuplot commands, while the latter syntax requires to be the only command on the line. Control will return immediately to `gnuplot` after this command is executed. For example, in AmigaOS, MS-DOS or OS/2,

 
      ! dir

or

 
      system "dir"

prints a directory listing and then returns to `gnuplot`.

Other examples of the former syntax:

 
       system "date"; set time; plot "a.dat"
       print=1; if (print) replot; set out; system "lpr x.ps"

On an Atari, the `!` command first checks whether a shell is already loaded and uses it, if available. This is practical if `gnuplot` is run from `gulam`, for example.


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2.23 splot

`splot` is the command for drawing 3-d plots (well, actually projections on a 2-d surface, but you knew that). It can create a plot from functions or a data file in a manner very similar to the `plot` command.

See `plot` for features common to the `plot` command; only differences are discussed in detail here. Note specifically `plot`'s `axes` option is not available for `splot`.

Syntax:

 
      splot {<ranges>}
            <function> | "<datafile>" {datafile-modifiers}}
            {<title-spec>} {with <style>}
            {, {definitions,} <function> ...}

where either a <function> or the name of a data file enclosed in quotes is supplied. The function can be a mathematical expression, or a triple of mathematical expressions in parametric mode.

By default `splot` draws the xy plane completely below the plotted data. The offset between the lowest ztic and the xy plane can be changed by ticslevel. The orientation of a `splot` projection is controlled by view. See view and ticslevel for more information.

The syntax for setting ranges on the `splot` command is the same as for `plot`. In non-parametric mode, the order in which ranges must be given is xrange, yrange, and zrange. In parametric mode, the order is urange, vrange, xrange, yrange, and zrange.

The `title` option is the same as in `plot`. The operation of with is also the same as in `plot`, except that the plotting styles available to `splot` are limited to `lines`, `points`, `linespoints`, `dots`, and `impulses`; the error-bar capabilities of `plot` are not available for `splot`.

The datafile options have more differences.

See also `show plot`.


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2.23.1 data-file

As for `plot`, discrete data contained in a file can be displayed by specifying the name of the data file, enclosed in quotes, on the `splot` command line.

Syntax:

 
      splot '<file_name>' {binary <binary list>}
                          {matrix}
                          {index <index list>}
                          {every <every list>}
                          {using <using list>}

The special filenames `""` and `"-"` are permitted, as in `plot`.

In brief, `binary` and `matrix` indicate that the data are in a special form, index selects which data sets in a multi-data-set file are to be plotted, every specifies which datalines (subsets) within a single data set are to be plotted, and using determines how the columns within a single record are to be interpreted.

The options index and every behave the same way as with `plot`; using does so also, except that the using list must provide three entries instead of two.

The `plot` options thru and smooth are not available for `splot`, but cntrparam and dgrid3d provide limited smoothing capabilities.

Data file organization is essentially the same as for `plot`, except that each point is an (x,y,z) triple. If only a single value is provided, it will be used for z, the datablock number will be used for y, and the index of the data point in the datablock will be used for x. If two or four values are provided, `gnuplot` uses the last value for calculating the color in pm3d plots. Three values are interpreted as an (x,y,z) triple. Additional values are generally used as errors, which can be used by `fit`.

Single blank records separate datablocks in a `splot` datafile; `splot` treats datablocks as the equivalent of function y-isolines. No line will join points separated by a blank record. If all datablocks contain the same number of points, `gnuplot` will draw cross-isolines between datablocks, connecting corresponding points. This is termed "grid data", and is required for drawing a surface, for contouring (contour) and hidden-line removal (hidden3d). See also `splot grid_data`.

It is no longer necessary to specify `parametric` mode for three-column `splot`s.


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2.23.1.1 binary matrix

Gnuplot can read matrix binary files by use of the option `binary` appearing without keyword qualifications unique to general binary, i.e., `array`, `record`, `format`, or `filetype`. Other general binary keywords for translation should also apply to matrix binary. (See `binary general` for more details.)

In previous versions, `gnuplot` dynamically detected binary data files. It is now necessary to specify the keyword `binary` directly after the filename.

Single precision floats are stored in a binary file as follows:

 
      <N+1>  <y0>   <y1>   <y2>  ...  <yN>
       <x0> <z0,0> <z0,1> <z0,2> ... <z0,N>
       <x1> <z1,0> <z1,1> <z1,2> ... <z1,N>
        :      :      :      :   ...    :

which are converted into triplets:

 
      <x0> <y0> <z0,0>
      <x0> <y1> <z0,1>
      <x0> <y2> <z0,2>
       :    :     :
      <x0> <yN> <z0,N>

 
      <x1> <y0> <z1,0>
      <x1> <y1> <z1,1>
       :    :     :

These triplets are then converted into `gnuplot` iso-curves and then `gnuplot` proceeds in the usual manner to do the rest of the plotting.

A collection of matrix and vector manipulation routines (in C) is provided in `binary.c`. The routine to write binary data is

 
      int fwrite_matrix(file,m,nrl,nrl,ncl,nch,row_title,column_title)

An example of using these routines is provided in the file `bf_test.c`, which generates binary files for the demo file `demo/binary.dem`.

The index keyword is not supported, since the file format allows only one surface per file. The every and using filters are supported. using operates as if the data were read in the above triplet form.

See also `binary general` and

Binary File Splot Demo.


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2.23.1.2 example datafile

A simple example of plotting a 3-d data file is

 
      splot 'datafile.dat'

where the file "datafile.dat" might contain:

 
      # The valley of the Gnu.
         0 0 10
         0 1 10
         0 2 10

 
         1 0 10
         1 1 5
         1 2 10

 
         2 0 10
         2 1 1
         2 2 10

 
         3 0 10
         3 1 0
         3 2 10

Note that "datafile.dat" defines a 4 by 3 grid ( 4 rows of 3 points each ). Rows (datablocks) are separated by blank records.

Note also that the x value is held constant within each dataline. If you instead keep y constant, and plot with hidden-line removal enabled, you will find that the surface is drawn 'inside-out'.

Actually for grid data it is not necessary to keep the x values constant within a datablock, nor is it necessary to keep the same sequence of y values. `gnuplot` requires only that the number of points be the same for each datablock. However since the surface mesh, from which contours are derived, connects sequentially corresponding points, the effect of an irregular grid on a surface plot is unpredictable and should be examined on a case-by-case basis.


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2.23.1.3 matrix_ascii

The `matrix` keyword (without a sequent `binary` keyword) in

 
    {s}plot 'a.dat' matrix

indicates that data are stored in an ascii numbers matrix format.

The z-values are read in a row at a time, i. e.,

 
    z11 z12 z13 z14 ...
    z21 z22 z23 z24 ...
    z31 z32 z33 z34 ...

and so forth.

In 3D, the x- and y-indices of the matrix surface plot correspond to column and row indices of the matrix, respectively, being enumerated from 0. You can rescale or transform the axes as usual for a data file with three columns by means of x=$1, y=$2, z=$3. For example

 
    splot 'a.dat' matrix using (1+$1/100):(1+$2*10):3

A blank line or comment line ends the matrix, and starts a new surface mesh. You can select among the meshes inside a file by the index option to the `splot` command, as usual.

See `matrix` for examples of plotting rows and columns of the matrix in a 2D plot.


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2.23.1.4 matrix

Datafile can be in an ascii or binary matrix format. The `matrix` flag indicates that the file is ascii, the `binary` or `matrix binary` stands for a binary format. For details, see `matrix ascii` and `matrix binary`.

Basic usage in `splot`:

 
    splot 'a.dat' matrix
    splot 'a.gpbin' {matrix} binary

Advanced usage in `splot`:

 
    splot 'a.dat' matrix using 1:2:3
    splot 'a.gpbin' {matrix} binary using 1:2:3

allows to transform the axes coordinates and the z-data independently.

Usage in `plot`:

 
    plot `a.dat` matrix
    plot `a.dat` matrix using 1:3
    plot 'a.gpbin' {matrix} binary using 1:3

will plot rows of the matrix, while using 2:3 will plot matrix columns, and using 1:2 the point coordinates (rather useless). Applying the every option you can specify explicit rows and columns.

Example - rescale axes of a matrix in an ascii file:

 
    splot `a.dat` matrix using (1+$1):(1+$2*10):3

Example - plot the 3rd row of a matrix in an ascii file:

 
    plot 'a.dat' matrix using 1:3 every 1:999:1:2

(rows are enumerated from 0, thus 2 instead of 3).


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2.23.2 grid data

The 3D routines are designed for points in a grid format, with one sample, datapoint, at each mesh intersection; the datapoints may originate from either evaluating a function, see isosamples, or reading a datafile, see datafile. The term "isoline" is applied to the mesh lines for both functions and data. Note that the mesh need not be rectangular in x and y, as it may be parameterized in u and v, see isosamples.

However, `gnuplot` does not require that format. In the case of functions, 'samples' need not be equal to 'isosamples', i.e., not every x-isoline sample need intersect a y-isoline. In the case of data files, if there are an equal number of scattered data points in each datablock, then "isolines" will connect the points in a datablock, and "cross-isolines" will connect the corresponding points in each datablock to generate a "surface". In either case, contour and hidden3d modes may give different plots than if the points were in the intended format. Scattered data can be converted to a {different} grid format with dgrid3d.

The contour code tests for z intensity along a line between a point on a y-isoline and the corresponding point in the next y-isoline. Thus a `splot` contour of a surface with samples on the x-isolines that do not coincide with a y-isoline intersection will ignore such samples. Try:

 
       set xrange [-pi/2:pi/2]; set yrange [-pi/2:pi/2]
       set style function lp
       set contour
       set isosamples 10,10; set samples 10,10;
       splot cos(x)*cos(y)
       set samples 4,10; replot
       set samples 10,4; replot


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2.23.3 splot overview

`splot` can display a surface as a collection of points, or by connecting those points. As with `plot`, the points may be read from a data file or result from evaluation of a function at specified intervals, see isosamples. The surface may be approximated by connecting the points with straight line segments, see surface, in which case the surface can be made opaque with `set hidden3d.` The orientation from which the 3d surface is viewed can be changed with view.

Additionally, for points in a grid format, `splot` can interpolate points having a common amplitude (see contour) and can then connect those new points to display contour lines, either directly with straight-line segments or smoothed lines (see cntrparam). Functions are already evaluated in a grid format, determined by isosamples and samples, while file data must either be in a grid format, as described in data-file, or be used to generate a grid (see dgrid3d).

Contour lines may be displayed either on the surface or projected onto the base. The base projections of the contour lines may be written to a file, and then read with `plot`, to take advantage of `plot`'s additional formatting capabilities.


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2.24 system

`system` spawns shell to execute a command. Please type shell for more details.


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2.25 test

This command graphically tests or presents terminal and palette capabilities.

Syntax:

 
      test {terminal | palette [rgb|rbg|grb|gbr|brg|bgr]}

test or `test terminal` creates a display of line and point styles and other useful things appropriate for and supported by the `terminal` you are just using.

palette draws graphically profiles R(z),G(z),B(z), where 0<=z<=1, as calculated by the current color palette. In other words, it is a beautiful plot you would have to do yourself with the result of `show palette palette 256 float`. The optional parameter, a permutation of letters rgb, determines the sequence of r,g,b profiles drawn one after the other -- try this yourself for `set palette gray`. The default sequence is rgb.


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2.26 unset

Options set using the `set` command may be returned to their default state by issuing the corresponding unset command.

Example:

 
      set xtics mirror rotate by -45 0,10,100
      ...
      unset xtics


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2.27 update

This command writes the current values of the fit parameters into the given file, formatted as an initial-value file (as described in the `fit`section). This is useful for saving the current values for later use or for restarting a converged or stopped fit.

Syntax:

 
      update <filename> {<filename>}

If a second filename is supplied, the updated values are written to this file, and the original parameter file is left unmodified.

Otherwise, if the file already exists, `gnuplot` first renames it by appending `.old` and then opens a new file. That is, "`update 'fred'`" behaves the same as "`!rename fred fred.old; update 'fred.old' 'fred'`". [On DOS and other systems that use the twelve-character "filename.ext" naming convention, "ext" will be "`old`" and "filename" will be related (hopefully recognizably) to the initial name. Renaming is not done at all on VMS systems, since they use file-versioning.]

Please see `fit` for more information.


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