hello jaime,
> My students are using Maxima 5.9.1 and I've copied into their disks
> plotdf.lisp, from share/contrib/ in the CVS repository.
>
> That file defines function "plotdf", but Maxima only recognizes PLOTDF:
maybe if you do plotdf: PLOTDF$ then plotdf (...) will have
the expected effect.
if there is only one copy of plotdf.lisp in question (i.e., the
students do not have their own copies) you might change
(defun $plotdf (...)) to (defun |$PLOTDF| (...)).
(not sure if that helps -- try that only if plotdf: PLOTDF$ doesn't work.)
sorry i can't be more helpful,
robert dodier