### 12.1 Introduction to Plotting

Maxima uses an external plotting package to make the plots (see the section on `Plotting Formats`). The plotting functions calculate a set of points and pass them to the plotting package together with a set of commands. That information can be passed to the external program either through a pipe or by calling the program with the name of a file where the data has been saved. The data file is given the name `maxout_xxx.format`, where `xxx` is a number that is unique to every concurrently-running instance of Maxima and `format` is the name of the plotting format being used (`gnuplot`, `xmaxima`, `mgnuplot`, `gnuplot_pipes` or `geomview`).

There are commands to save the plot in a graphic format file. In those cases, the file `maxout_xxx.format` created by Maxima includes commands that will make the external plotting program save the result in a graphic file. The default name for that graphic file is `maxplot.extension`, where `extension` is the extension normally used for the kind of graphic file selected.

The `maxout_xxx.format` and `maxplot.extension` files are created in the directory specified by the system variable `maxima_tempdir`. That location can be changed by assigning to that variable (or to the environment variable `MAXIMA_TEMPDIR`) a string that represents a valid directory where Maxima can create new files. The output of the Maxima plotting command will be a list with the names of the file(s) created, including their complete path.

If the format used is either `gnuplot` or `xmaxima`, the external programs `gnuplot` or `xmaxima` can be run, giving it the file `maxout_xxx.format` as argument, in order to view again a plot previously created in Maxima. Thus, when a Maxima plotting command fails, the format can be set to `gnuplot` or `xmaxima` and the plain-text file `maxout_xxx.gnuplot` (or `maxout_xxx.xmaxima`) can be inspected to look for the source of the problem.

The additional package draw provides functions similar to the ones described in this section with some extra features. Note that some plotting options have the same name in both plotting packages, but their syntax and behavior is different. To view the documentation for a graphic option `opt`, type `?? opt` in order to choose the information for either of those two packages.

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Categories: Plotting