Gnuplot

A pipe-based interface to the gnuplot plotting program.

This is the main module of the Gnuplot package.

Written by Michael Haggerty. Inspired by and partly derived from an earlier version by Konrad Hinsen. If you find a problem or have a suggestion, please let me know. Other feedback would also be appreciated.

The Gnuplot.py home page is at

Gnuplot.py

For information about how to use this module:

1. Check the README file.

2. Look at the example code in demo.py and try running it by typing python demo.py or python __init__.py.

3. For more details see the extensive documentation strings throughout the python source files, especially this file, _Gnuplot.py, PlotItems.py, and gp_unix.py.

4. The docstrings have also been turned into html which can be read here. However, the formatting is not perfect; when in doubt, double-check the docstrings.

You should import this file with import Gnuplot, not with from Gnuplot import *, because the module and the main class have the same name, `Gnuplot'.

To obtain the gnuplot plotting program itself, see the gnuplot FAQ. Obviously you need to have gnuplot installed if you want to use Gnuplot.py.

The old command-based interface to gnuplot has been separated out into a separate module, oldplot.py. If you are still using that interface you should import Gnuplot.oldplot; otherwise you should stick to the more flexible object-oriented interface contained here.

Features:

• Allows the creation of two or three dimensional plots from python.

• A gnuplot session is an instance of class Gnuplot. Multiple sessions can be open at once. For example::

          g1 = Gnuplot.Gnuplot()
          g2 = Gnuplot.Gnuplot()
  
      Note that due to limitations on those platforms, opening multiple
      simultaneous sessions on Windows or Macintosh may not work
      correctly.  (Feedback?)
  
  

• The implicitly-generated gnuplot commands can be stored to a file instead of executed immediately::

          g = Gnuplot.Gnuplot('commands.txt')
  
      The 'commands.txt' file can then be run later with gnuplot's
      'load' command.  Beware, however: the plot commands may depend on
      the existence of temporary files, which will probably be deleted
      before you use the command file.
  
  

• Can pass arbitrary commands to the gnuplot command interpreter::

          g('set pointsize 2')
  
      (If this is all you want to do, you might consider using the
      lightweight GnuplotProcess class defined in gp.py.)
  
  

• A Gnuplot object knows how to plot objects of type PlotItem. Any PlotItem can have optional title and/or with suboptions. Builtin PlotItem types:

  • Data(array1) -- data from a Python list or NumPy array (permits additional option cols )

  • 'File(filename)' -- data from an existing data file (permits additional option using )

  • 'Func(exp(4.0 * sin(x)))' -- functions (passed as a string, evaluated by gnuplot)

  • GridData(m, x, y) -- data tabulated on a grid of (x,y) values (usually to be plotted in 3-D)

  See the documentation strings for those classes for more details.

• PlotItems are implemented as objects that can be assigned to variables and plotted repeatedly. Most of their plot options can also be changed with the new set_option() member functions then they can be replotted with their new options.

• Communication of commands to gnuplot is via a one-way pipe. Communication of data from python to gnuplot is via inline data (through the command pipe) or via temporary files. Temp files are deleted automatically when their associated PlotItem is deleted. The PlotItems in use by a Gnuplot object at any given time are stored in an internal list so that they won't be deleted prematurely.

• Can use replot method to add datasets to an existing plot.

• Can make persistent gnuplot windows by using the constructor option persist=1. Such windows stay around even after the gnuplot program is exited. Note that only newer version of gnuplot support this option.

• Can plot either directly to a postscript printer or to a postscript file via the hardcopy method.

• Grid data for the splot command can be sent to gnuplot in binary format, saving time and disk space.

• Should work under Unix, Macintosh, and Windows.

Restrictions:

• Relies on the Numeric Python extension. This can be obtained from SourceForge. If you're interested in gnuplot, you would probably also want NumPy anyway.

• Only a small fraction of gnuplot functionality is implemented as explicit method functions. However, you can give arbitrary commands to gnuplot manually::

          g = Gnuplot.Gnuplot()
          g('set data style linespoints')
          g('set pointsize 5')
  
  

• There is no provision for missing data points in array data (which gnuplot allows via the set missing command).

Bugs:

• No attempt is made to check for errors reported by gnuplot. On unix any gnuplot error messages simply appear on stderr. (I don't know what happens under Windows.)

• All of these classes perform their resource deallocation when __del__ is called. Normally this works fine, but there are well-known cases when Python's automatic resource deallocation fails, which can leave temporary files around.