title: statsmodels' mosaic plot with empty values
body: <p>I would like to create a mosaic plot with <a href="http://statsmodels.sourceforge.net/stable/generated/statsmodels.graphics.mosaicplot.mosaic.html" rel="nofollow noreferrer"><code>statsmodels.graphics.mosaicplot.mosaic()</code></a> with data that casts empty cells.  They look ugly in the resulting plot, because a cell is created irrespective of its size.</p>
  
  <p>Example:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  
  import pandas as pd
  from statsmodels.graphics.mosaicplot import mosaic
  
  df = pd.DataFrame({'size' : ['small', 'large', 'large'],
                     'length' : ['long', 'short', 'long']})
  
  print(df)  # note that the 'short'-'small' combination is missing
  
  fig = plt.figure()
  ax = fig.add_subplot(111)
  mosaic(df, ax=ax)
  </code></pre>
  
  <p>creates a plot with an empty cell for value "short small":</p>
  
  <p><a href="https://i.stack.imgur.com/5V8pH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5V8pH.png" alt="enter image description here"></a></p>
  
  <p>Is there a way to either avoid the creation of this cell or to remove it from the plot afterwards?</p>