title: matplotlib - producing boxplots in a loop
body: <p>I'd like to plot several boxplots in one figure, on one axis. The data that I use for the boxplots, however, is too large to be read into memory at once. So I read it in chunks using pandas read_csv(). What I would like to do is to produce some boxplots in each iteration and add the new boxplots from iteration i to the same figure as the boxplots from iteration i-1, wihtout holding on to the data of iteration i-1.</p>
  
  <p>I want to stress, that I do not need to update the data for an already existing boxplot. It's more like I get a new data column with each iteration and I want to display a boxplot of that column next to the existing boxplot. </p>
  
  <p>E.g.: Say I have </p>
  
  <pre><code>df = pd.DataFrame(np.random.rand(100,2))
  </code></pre>
  
  <p>Assume that I could read the columns only one after the other. How do I add the boxplot of the second column to the already existing boxplot of the first column to have the same result as ax.boxplot(df.values)?</p>