No plotting in matplotlib after version upgrade
Question: I just updated matplotlib to 1.1.0 on a server running ubuntu 10.04 LTS in
order to play better with pandas. Pandas was converting my index according the
functionality of a different version of matplotlib. I installed on one server
using "easyinstall -U matplotlib" and "pip install -U matplotlib" on the
other.

I cannot plot in any of my previous working scripts or in ipython. show() has
stopped working in pylab. Could someone point me in the direction of what may
be broken?

I took the following test script "simple_plot.py" from matplotlib's site and
tested it on various servers after first deleting my config directory.

    
    
    from pylab import *
    plot([1,2,3])
    show()
    

simple_plot produces a plot on all servers that are running on versions <=
0.99 but has no output on version 1.1.

here is the debug output on one server that does not work:

    
    
    $HOME=/home/michael
    CONFIGDIR=/home/michael/.matplotlib
    matplotlib data path /usr/local/lib/python2.6/dist-packages/matplotlib-1.1.0-py2.6-linux-x86_64.egg/matplotlib/mpl-data
    loaded rc file /usr/local/lib/python2.6/dist-packages/matplotlib-1.1.0-py2.6-linux-x86_64.egg/matplotlib/mpl-data/matplotlibrc
    matplotlib version 1.1.0
    verbose.level debug
    interactive is False
    platform is linux2
    Using fontManager instance from /home/michael/.matplotlib/fontList.cache
    backend agg version v2.2
    python version:2.6.5
    findfont: Matching :family=sans-serif:style=normal:variant=normal:weight=normal:stretch=normal:size=medium to Bitstream Vera Sans (/usr/local/lib/python2.6/dist-packages/matplotlib-1.1.0-py2.6-linux- x86_64.egg/matplotlib/mpl-data/fonts/ttf/Vera.ttf) with score of 0.000000
    


Answer: You are using the Agg backend, which does not show the figure on the display.
This is the default for matplotlib. You need to change your backend in your
matplotlib configuration file (usually ~/.matplotlib/matplotlibrc). Look for
the part:

    
    
    backend      : Agg
    

And replace 'Agg' with one of: GTKAgg, Qt4Agg, TkAgg, WXAgg. You may not have
all of these (or any!) installed in your system, so try one that works.

If you don't have the file ~/.matplotlib/matplotlibrc, then copy it from your
main configuration:

    
    
    cp /usr/local/lib/python2.6/dist-packages/matplotlib-1.1.0-py2.6-linux-x86_64.egg/matplotlib/mpl-data/matplotlibrc ~/.matplotlib/matplotlibrc
    

