ubuntu: uninstall matplotlib with pip won't work

I'm on Ubuntu and I neeed to uninstallmatplotlib, which I installed as an ubuntu package and later upgraded with pip. The usual command doesn't work:

$ sudo pip uninstall matplotlibCan't uninstall 'matplotlib'. No files were found to uninstall.

What should I do?

Extra info:

~$ pip matplotlib --versionERROR: unknown command "matplotlib"me@me:~$ pip show matplotlib---Name: matplotlibVersion: 1.4.0Location: /usr/local/lib/python2.7/dist-packagesRequires: numpy, six, python-dateutil, pyparsing, nose, mock, nose, mock$ pip --versionpip 1.5.4 from /usr/lib/python2.7/dist-packages (python 2.7)