title: getting pandas Setting With Enlargement right
body: <p>Since version 0.13, it is possible to append to a dataframe by referring to indices in .loc or .ix which are not yet in the dataframe. See the <a href="http://pandas.pydata.org/pandas-docs/stable/indexing.html#setting-with-enlargement" rel="nofollow">documentation</a>.</p>
  
  <p>Then I am confused why this line fails:</p>
  
  <pre><code>all_treatments.loc[originalN:newN,:]    = all_treatments.loc[0:newrowcount,:]
  </code></pre>
  
  <p>This generates a ValueError:</p>
  
  <pre><code>ValueError: could not broadcast input array from shape (12) into shape (0)
  </code></pre>
  
  <p>Here <code>all_treatments.shape = (53, 12)</code>, <code>originalN = 53</code>, <code>newN = 64</code>, <code>all_treatments.loc[originalN:newN,:].shape = (0,12)</code>, <code>all_treatments.loc[0:newrowcount,:].shape = (12,12)</code>.</p>
  
  <p>What is the proper way to set with enlargement here?</p>