I've been learning me some R lately. If you're not familiar, R is a statistical analysis program, particularly know for it's strong graphical outputs. The program actually gves you all the options you'd need to do pretty much everything you could imagine, though I've found it quite useful and definitely faster and easier to export a basic plot as an SVG and then attack it in Inkscape. Being able to see what you're doing rather than trying to place labels with command-line controls has obvious benefits.

Here's what I started with from R:



Before using Inkscape to transform it into:



and