title: Polar contour plot in Matplotlib
body: <p>I have a set of data that I want to use to produce a contour plot in polar co-ordinates using Matplotlib.</p>
  
  <p>My data is the following:</p>
  
  <ul>
  <li><code>theta</code> - 1D array of angle values</li>
  <li><code>radius</code> - 1D array of radius values</li>
  <li><code>value</code> - 1D array of values that I want to use for the contours</li>
  </ul>
  
  <p>These are all 1D arrays that align properly - eg:</p>
  
  <pre><code>theta   radius   value
  30      1        2.9
  30      2        5.3
  35      5        9.2
  </code></pre>
  
  <p>That is, all of the values are repeated enough times so that each row of this 'table' of three variables defines one point.</p>
  
  <p>How can I create a polar contour plot from these values? I've thought about converting the radius and theta values to x and y values and doing it in cartesian co-ordinates, but the contour function seems to require 2D arrays, and I can't quite understand why.</p>
  
  <p>Any ideas?</p>