title: Shifted colorbar matplotlib
body: <p>I am trying to make a filled contour for a dataset. It should be fairly straightforward:</p>
  
  <pre><code>plt.contourf(x, y, z, label = 'blah', cm = matplotlib.cm.RdBu)
  </code></pre>
  
  <p>However, what do I do if my dataset is not symmetric about 0? Let's say I want to go from blue (negative values) to 0 (white), to red (positive values). If my dataset goes from -8 to 3, then the white part of the color bar, which should be at 0, is in fact slightly negative. Is there some way to shift the color bar?</p>