New package for drawing direction fields with gnuplot

Seems like a useful package, since it makes it possible to
draw direction fields with formats other than Openmath.
I'm inclined to include it. Other opinions?

In any event, thanks for your efforts, Mark.

best

Robert Dodier

On 11/16/10, Mark H Weaver <mhw at netris.org> wrote:
> Hello all,
>
> I have created a new package, drawdf, for drawing direction fields
> using Maxima and gnuplot.  Although it lacks the interactive
> convenience of plotdf, it is far more flexible and produces nicer
> looking results.  It also has better integration with wxMaxima and
> Imaxima, allowing inline plots via wxdrawdf.
>
> For a brief demonstration of drawdf's capabilities, please see:
>
>    http://www.netris.org/~mhw/maxima/drawdf-demo.html
>
> Note that drawdf is built upon the draw package, and passes very long
> lists of graphic objects to draw2d.  This exposes a scalability
> problem with draw2d, namely that it requires stack space proportional
> to the number of graphic objects.  Fortunately, the fix is simple.
> Just replace the recursive definition of draw-transform in draw.lisp
> with the following iterative version:
>
> (defun draw-transform (expr transform)
>   (reduce #'append
>           (mapcar #'(lambda (x) (draw-transform-one x transform))
>                   expr)
>           :from-end t))
>
> Drawdf is part of my recent work supporting the use of Maxima in two
> classes on differential equations at Brown University, and more
> importantly in an upcoming textbook by Vladimir Dobrushkin, due out
> next year.  However, the textbook can only describe commands which are
> included in the official Maxima release.
>
> With that in mind, is there any chance drawdf (plus the above fix)
> could be included in the next Maxima release? :)
>
> Comments and suggestions are of course welcome.
>
>      Best,
>       Mark
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