title: descriptive stats for two categorical variables (pandas)
body: <p>I need to get the mean and median for frequencies between two categorical variables. E.g.:</p>
  
  <p><strong>Label Letter Num</strong>
  <br />Foo | A | 1
  <br />Foo | B | 2
  <br />Foo | C | 4
  <br />Bar | A | 2
  <br />Bar | G | 3
  <br />Bar | N | 1
  <br />Bar | P | 2
  <br />Cee | B | 1
  <br />Cee | B | 2
  <br />Cee | C | 4
  <br />Cee | D | 5</p>
  
  <p>For instance, what's the mean and median number of letters per label. Here there are 11 cases out of three possible labels (M=3.667) and the median is 4 (3 foo, 4 bar, 4 cee). How can I calculate this in pandas. Is it possible to do this with a groupby statement?  My data set is much larger than this. </p>