title: Altering height range of matplotlib histogram2d
body: <p>I am trying to plot some 2D empirical probability distributions using matplotlib's histogram2d. I want the colours to be on the same scale across several different plots, but cannot find a way to set a scale even if I know a global upper and lower bound on the resulting distribution. As is, each color scale will run from the minimum height to the maximum height of the histogram bins, but this range will be different for each plot.</p>
  
  <p>One potential solution would be to force one bin to take the height of my lower bound, and another my upper bound. Even this does not seem like a very straight forward task. </p>