title: convert "meshvectors" to meshgrid in Python
body: <p>I have three 1D vectors, first two are coordinates and third is a value. I can't figure out a simple way to plot them using <code>pcolor</code> or <code>imshow</code> because these functions accept the <strong>meshgrid</strong> values, and the funny thing is that my vectors are already a vector representation of <strong>meshgrid</strong>:</p>
  
  <pre><code>csv_data=StringIO("""subsample, colsample, val
       0.6, 0.6, 0.87277
       0.7, 0.6, 0.87408
       0.8, 0.6, 0.87294
       0.9, 0.6, 0.87242
       0.6, 0.7, 0.87341
       0.7, 0.7, 0.87238
       0.8, 0.7, 0.87290
       0.9, 0.7, 0.87285
       0.6, 0.8, 0.87268
       0.7, 0.8, 0.87392
       0.8, 0.8, 0.87353
       0.9, 0.8, 0.87223
       0.6, 0.9, 0.87147
       0.7, 0.9, 0.87271
       0.8, 0.9, 0.87247
       0.9, 0.9, 0.87324
      """)
  
  df = pd.read_csv(csv_data, sep=', ')
  
  X, Y, Z = df.subsample.values, df.colsample.values, df.val.values
  </code></pre>
  
  <p>As you can see for each value of X there is a full set of Y values. And for each value of Y there is a complete set of X values with Z already calculated. How can I construct x, y and z as meshgrids based on this data?</p>