plotting syntax



Hello,

  I would like to define a simple function to dynamically set ranges
  with plot2d.

  I know draw2d in in the works, but I am teaching a
  class now in which the students are using maxima in Windows. I don't
  know how to tell them how to get and use draw2d.

Consider the following

(%i17) yrange_20: [gnuplot_preamble, [ " set yrange [-20:20] " ]];
(%o17)            [gnuplot_preamble, [ set yrange [-20:20] ]]
(%i18) plot2d(x^2/(x+1), [x,-2,2], yrange_20);

This works fine.

Now, I would like to have 'yrange_20' as a function.

For instance,

%i19) yrange(a): [gnuplot_preamble, [ " set yrange [-a:a] " ]];

Improper value assignment:
yrange(a)
  -- an error.  To debug this try debugmode(true);

I can't get the 'a' to be put inside the double quotes so the y range
can be dynamically set.

Any ideas?

TIA,
  -sen

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  | Sheldon E. Newhouse            |    e-mail: sen1 at math.msu.edu           |
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