title: shading and masking over pcolor in matlab
body: <p>Two questions really, but I feel they overlap, so I'll ask them in one place (if that's OK).</p>
  
  <p>I've created a pcolor in matlab using:</p>
  
  <pre><code>p = pcolor(Lon', Lat', data);
  </code></pre>
  
  <p>But now I want to add some information.  I have a matrix <code>mask</code> which has the same dimensions as data, but is populated by 1s and 0s.  Where it contains a 1, I would like to retain the pixel in the pcolor, and when it contains a 0, remove it (not just turn the value to zero, which is not represented by a white pixel in my colormap).</p>
  
  <p>Secondly, I have a second matrix, called 'stipple', which again contains 0s and 1s.  I now want to overlay any location represented by a 1 with a stipple effect.</p>
  
  <p>The purpose of this is to create an image something like this:
  <a href="http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-spm-7.html" rel="nofollow">http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-spm-7.html</a>
  where the average is painted on, but areas where there is too much disagreement are whited out, and areas where there is much agreement are 'stippled'.</p>
  
  <p>Thanks in advance!</p>