title: Boxplot stratified by column in python pandas
body: <p>I would like to draw a boxplot for the following pandas dataframe:</p>
  
  <pre><code>&gt; p1.head(10)
  
     N0_YLDF    MAT
  0     1.29  13.67
  1     2.32  10.67
  2     6.24  11.29
  3     5.34  21.29
  4     6.35  41.67
  5     5.35  91.67
  6     9.32  21.52
  7     6.32  31.52
  8     3.33  13.52
  9     4.56  44.52
  </code></pre>
  
  <p>I want the boxplots to be of the column 'N0_YLDF', but they should be stratified by 'MAT'. When I use the foll. command:</p>
  
  <pre><code>p1.boxplot(column='N0_YLDF',by='MAT')
  </code></pre>
  
  <p>It uses all the unique MAT values, which in the full p1 dataframe number around 15,000. This results in an incomprehensible boxplot.</p>
  
  <p>Is there any way I can stratify the MAT values, so that I get a different boxplot of N0_YLDF for the first quartile of MAT values and so on....</p>
  
  <p>thanks!</p>