Hello. First of all, a big thanks for this great tool!
The instructions for installation of matplotlib in Debian at matplotlib website are a bit outdated. It recommends to add a new package repository to /etc/apt/sources.list. But this repository is completely outdated (latest matplotlib version there is 0.82).
Debian has already accepted python-matplotlib into the package system (testing and unstable), there is no need to add repositories.
Installing mpl on testing and unstable is just:
apt-get install python-matplotlib
For stable I’d suggest the user to use packages from testing instead of 0.82. Or adding a more updated repository.