I've been looking for a feature that I don't see - something similar to pgplot's PGAXIS routine, which draws an axis from one arbitrary point to another, with arbitrary scaling. I apologize if I simply missed it, but if it's not there it might go on a wish list.
Thanks to the many developers of this fine package, by the way. I've been looking around for something I can use when my beloved pgplot finally dies, and this looks like it'll do very nicely.
Alan W. Irwin
Try http://plplot.sourceforge.net/docbook-manual/plplot-html-5.9.7/plaxes.html. It may be possible to suppress the box part of it (which I assume is what you want) by careful choice of the options strings, but I haven't tried this myself.