This is great! I have been using iPython notebook (as a biologist) for some months now and "getting a feel for the data" is very important. This notebook is littered with handy Python one liners to quickly gain insight into the data.

I love iPython notebook, I can run the entire back-end on our cluster while working with terabytes of data on my laptop tethered to my phone from a moving train (as we speak ;)).

Edit: Now using your code directly on my own data, I'm learning a lot, a big thanks to Randal S. Olson!!