title: Heatmap in matplotlib with pcolor?
body: <p>I'd like to make a heatmap like this (shown on <a href="http://flowingdata.com/2010/01/21/how-to-make-a-heatmap-a-quick-and-easy-solution/" rel="noreferrer">FlowingData</a>):
  <img src="https://i.stack.imgur.com/pjnUL.png" alt="heatmap"></p>
  
  <p>The source data is <a href="http://datasets.flowingdata.com/ppg2008.csv" rel="noreferrer">here</a>, but random data and labels would be fine to use, i.e.</p>
  
  <pre><code>import numpy
  column_labels = list('ABCD')
  row_labels = list('WXYZ')
  data = numpy.random.rand(4,4)
  </code></pre>
  
  <p>Making the heatmap is easy enough in matplotlib:</p>
  
  <pre><code>from matplotlib import pyplot as plt
  heatmap = plt.pcolor(data)
  </code></pre>
  
  <p>And I even found a <a href="http://www.scipy.org/Cookbook/Matplotlib/Show_colormaps" rel="noreferrer">colormap</a> arguments that look about right: <code>heatmap = plt.pcolor(data, cmap=matplotlib.cm.Blues)</code></p>
  
  <p>But beyond that, I can't figure out how to display labels for the columns and rows and display the data in the proper orientation (origin at the top left instead of bottom left).</p>
  
  <p>Attempts to manipulate <code>heatmap.axes</code> (e.g. <code>heatmap.axes.set_xticklabels = column_labels</code>) have all failed. What am I missing here?</p>