My students aren't allowed to use Excel for graphing. It is so clunky it leads to bad science. wink

I'd never heard of Octave. It looks like it might serve.

If you're graphing simple data sets, then I'd recommend Origin and Kaleidagraph, though neither are free. (Big data sets need something more hefty.) If you're graphing functions, then Mathematica might be the right thing, though I don't use it to do that.