Ciao Lorenzo,
In addition to Robert's answer, this is another solution that should work in
5.9.1:
http://www.math.utexas.edu/pipermail/maxima/2005/009964.html
Let me know if you need some refinement of this basic code.
Mario
>
> Good news, bad news wrt plotting. Bad news: openplot_curves
> may well be broken. Good news: support for plotting discrete
> points was recently added to plot2d. Bad news: discrete
> point support isn't in 5.9.1 and it doesn't appear to be
> possible to simply load("plot.lisp") to get the new version
> (due to other changes in plot.lisp). Neutral news: it is
> possible to plot discrete points in 5.9.1 plot2d by a
> crufty hack; see "How do I plot a list of points?" at
> http://maxima.sf.net/wiki/index.php/Maxima%20helpful%20hints
>
> The documentation for plot2d was updated recently.
> See "Definitions for Plotting" at
> http://maxima.sourceforge.net/docs/original/maxima_toc.html
>
> > Furthermore, can Maxima save the 2 columns both
> > separately and together in order to be read as a
> > matrix by another plotting tool?
>
--
--------------------------
Mario Rodriguez Riotorto
www.biomates.net