Looking for a grapher
I'm looking for a program that can graph/plot equations and do basic things like find/graph derivatives. I've done a lot of searching on Sourceforge and Google, but I'm getting a lot of junk results.
I need something that is fairly feature-full, free and works on either Windows XP or Ubuntu (7.04 the 64 bit version). I'd prefer something on Ubuntu though... I set it up a few days ago and I've made the transition for the most part only going back to Windows once in a while.