title: How to apply quantile to pandas groupby object?
body: <p>I have a pandas groupby object called <code>grouped</code>. I can get <code>grouped.mean()</code> and other simple functions to work, but I cannot get <code>grouped.quantile()</code> to work. I get the following error when attempting to run <code>grouped.quantile()</code>:</p>
  
  <pre><code>ValueError: ('invalid literal for float(): groupA', u'occurred at index groups')
  </code></pre>
  
  <p>I am grouping by text labels, so I am not sure why the function tries to convert it to a float. It should be computing the quantile using the floats within each group. Can someone help to point out what I am doing wrong?</p>