Creating Charts

John Hunter jdhunter at ace.bsd.uchicago.edu
Wed Mar 31 14:51:46 CEST 2004


>>>>> "Thomas" == Thomas Guettler <guettli at thomas-guettler.de> writes:

    Thomas> Hi!  I need to create some simple charts with python.  A
    Thomas> list contains integers between 0 and mymax.

    Thomas> I want to see how the values are distributed (How many are
    Thomas> 0, how many are mymax, ...). The result should be a small
    Thomas> (200x200) png file.

    Thomas> matplotlib: Too much gtk binding (I only need a png) -

The web page may have given this impression, but it's not correct.
matplotlib is totally independent of GTK.  It *can* render to GTK, but
it isn't required.  GTK was the first matplotlib backend and perhaps
this is why is gets so much prominence on the web page.  But now you
can use it with GTK, WX or Tk, or none of the above to simply generate
PNG or PS figures.

To render to PNG w/o a GUI, use the antigrain (agg) backend as
described at http://matplotlib.sourceforge.net/backends.html#Agg.

Basically, you just need 

  * Download the src distribution, edit setup.py and set BUILD_AGG =
    True, do a normal setup.py install.

  * Edit the config file to make agg your default backend by setting

      backend      : Agg

    in your matplotlibrc file; see
    http://matplotlib.sourceforge.net/.matplotlibrc.  This file should
    be placed in your HOME dir.

Then you can make your small histogram figure as follows

    from matplotlib.matlab import *
    x = someInts   # your data here
    hist(x, 100)   # 100 is the number of histogram bins
    savefig('myfig.png', figsize=(4,4))    # figsize in inches

Hope this helps,
John Hunter




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