Cactus Code Thorn Gnuplot
Authors    : Gerd Lanfermann
CVS info   : $Header$
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Purpose of the thorn:

The thorn invokes gnuplot to plot a data file into a jpeg.

Requirements:

  - gnuplot in the path

Use as: 

  gnuplot(<datafile>,<imagefile>,[options1],[options2])

  where 
  - datafile   = name of the datafile to plot ( format: x y );
	         can be NULL
  - imagefile  = name of the image file (current format jpeg)
  - options1   = gnuplot options which go BEFORE the datafile in a gnuplot command
                 e.g. the range specification; can be NULL
  - options2   = gnuplot options which go AFTER  the datafile in a gnuplot command
                 e.g. line styles; can be NULL

Notes:

  You can omit the datafile if you want to plot functions, etc. which can go into
  options1/2.


Returns:

  negative number if failed

Examples:

retval = gnuplot("/home/me/data.xl", "/home/me/data.jpg", NULL, NULL);

retval = gnuplot("/home/me/data.xl", "/home/me/data.jpg", "[0:36]", "with lines");

retval = gnuplot(NULL, "/home/me/graph.jpg", "1/(x)", NULL);