title: 'module' object has no attribute 'DataFrame'
body: <p>For the following code:</p>
  <pre><code>import pandas as pd
  df = pd.DataFrame(np.random.rand(12,2), columns=['Apples', 'Oranges'] )
  df['Categories'] = pd.Series(list('AAAABBBBCCCC'))
  pd.options.display.mpl_style = 'default'
  df.boxplot(by='Categories')
  </code></pre>
  <p>I get the error:</p>
  <pre><code>'pandas' object has no attribute 'DataFrame'.
  </code></pre>
  <p>Any ideas on what is happening and how to fix this problem?</p>