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MathGroup Archive 1995

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Re: Mathlink & Graphics....

  • To: mathgroup at smc.vnet.net
  • Subject: [mg2228] Re: Mathlink & Graphics....
  • From: wagner at goober.cs.colorado.edu (Dave Wagner)
  • Date: Tue, 17 Oct 1995 02:34:56 -0400
  • Organization: University of Colorado, Boulder

In article <45d1sc$63m at ralph.vnet.net>,
The GodFather <gandalf at dogbert.ugcs.caltech.edu> wrote:
>
>	Unix Platform....
>
>	I've been trying to do this for a bit of time....
>
>	Basically, I would like from a C-code, to generate
>	a list of numbers {{1,2},{2,1}} and plot their positions
>	using mathematica's handy plotting routines....
>
>	If someone could post a way to simply execute a 
>	Plot[x^2,{x,-2,2}], and either have mathematica display
>	it (in X), or return PostScript to the link stream or
>	to an output file I would be extremely grateful....
>
>	An example of the type of thing I'm trying to do....
>
>	from within C-code:
>
>	MLPutFunction(link,"Extend",1); 
>	PutString(link,"Plot[x^2,{x,-2,2});
>	
>	If there was some way of setting the DisplayFunction
>	so mathematica would then just plot this thing out 'twould
>	be beautiful.  If there was some way I could get it to
>	output the plot to a postscript file, I would be joyous.
>	If there was any way I could get useable output, basically
>	I would be dancing around for weeks....
>
>	with much appreciation,
>
>	-John Joseph

You can redirect the PostScript output of a plotting command by overriding
DisplayFunction.  The default setting for DisplayFunction is $DisplayFunction,
which is

In[33]:=
    $DisplayFunction
Out[33]=
    Display[$Display,#1]&

This function is applied to the Graphics object that is generated by
the plot command.  Display is a built-in function that sends graphics
to a particular place:

In[34]:=
?Display

    Display[channel, graphics] writes graphics or sound to the
    specified output channel.

The default value for $Display is:

In[35]:=
    $Display
Out[35]=
    stdout

so, you can accomplish what you want to do by (a) opening a stream to
a file in Mathematica, (b) one of the following:

	- set $Display to that stream
	- set $DisplayFunction to Display[stream, #]&
	- use the option DisplayFunction:>Display[stream, #]& in
	  your plotting command.  This is probably the best option
	  since you'll undoubtedly want to use a different stream
	  for each plot.

Note that the contents of the file with be Mathematica-ese PostScript,
which isn't interpretable by most PostScript interpreters, I don't think.
There's a UNIX program that can do it that's distributed on MathSource,
I believe.

Let me know if this makes you dance...

		Dave Wagner
		Principia Consulting
		(303) 786-8371
		dbwagner at princon.com
		http://www.princon.com/princon


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