# [Maxima] plotting and solving inequalities

Mario Rodriguez biomates at telefonica.net
Sat Feb 24 16:59:31 CST 2007

```Hello,

> That is a nice and useful interface to gnuplot, but i see that
> you set the x range explicitly in your examples.
> I would like to enter the command
>
>  plot2d(x/(x^2-4));
>
> to display a plot, say, in the xrange [-3,3] and yrange [-6,6]
> (that is in the range needed to get the main pattern of the function,
> where relative changes are over a threshold - the first derivative
> could help to assess such range)
> and two vertical dotted lines at x=+2 x=-2.
>

Well, this could be investigated, but I don't know if there exists a
general acceptable solution; for example, what should be the main
pattern for periodic functions?

> How it that possible using draw2d?
>

Both in draw2d and in plot2d you must explicitly set the range for x.

> I have loaded your  draw.lisp  in maxima (version 5.10) but it fails o
> execute your example command (see below).
> Probably i should upgrade my maxima program
>
> thank you for you help
>
> --
> Pol
>
> ---- enc
>
> (%i8) draw2d(explicit(u^2,u,-3,3))\$
>
>   Maxima encountered a Lisp error:
>
>    Error in COND [or a callee]: The function CHECK-GNUPLOT-PROCESS is
> undefined.
>
>    Automatically continuing.
>    To reenable the Lisp debugger set *debugger-hook* to nil.

Oh sorry, the draw package needs the piping functions not present in
5.10; they are now in the repository version.

You have three options:

(draw_pipes:false;) before calling draw2d.

b) forget the draw package and make your plots with plot2d; in this
case, you can play with something like the following:

plot2d([x/(x^2-4),
[parametric, 2, t, [t,-5,5]],
[parametric, -2, t, [t,-5,5]]],[x,-5,5],
[gnuplot_curve_styles,
["with lines",
"with lines lt 0",
"with lines lt 0"]],
[gnuplot_preamble,
"set yrange [-5:5];set zeroaxis xy"] )\$

c) If you don't have anything better to do this weekend, try to compile
cvs maxima.

Molta sorte!

--
Mario Rodriguez Riotorto
www.biomates.net
```