title: mosaic plot with percentage and count values as labels in pandas DF
body: <p>I have pandas dataframe like this:</p>
  
  <pre><code>     LEVEL_1      LEVEL_2    Freq  Percentage
  0       HIGH          HIGH   8842      17.684
  1    AVERAGE           LOW   2802       5.604
  2        LOW           LOW  22198      44.396
  3    AVERAGE       AVERAGE   6804      13.608
  4        LOW       AVERAGE   2030       4.060
  5       HIGH       AVERAGE   3666       7.332
  6    AVERAGE          HIGH   2887       5.774
  7        LOW          HIGH    771       1.542
  </code></pre>
  
  <p>I can get tiles of LEVEL_1 and LEVEL_2:</p>
  
  <pre><code> from statsmodels.graphics.mosaicplot import mosaic
   mosaic(df, ['LEVEL_1','LEVEL_2'])
  </code></pre>
  
  <p><a href="http://i.stack.imgur.com/1J9Qi.png" rel="nofollow">enter image description here</a><br>
  I just want to put Freq and Percentage at the center of each tile of mosaic plot.
  How can I do this?</p>