title: Finding the row with the highest average in a numpy array
body: <p>Given the following array:</p>
  
  <pre><code>complete_matrix = numpy.array([
      [0, 1, 2, 4],
      [1, 0, 3, 5],
      [2, 3, 0, 6],
      [4, 5, 6, 0]])
  </code></pre>
  
  <p>I would like to identify the row with the highest average, excluding the diagonal zeros.
  So, in this case, I would be able to identify <code>complete_matrix[:,3]</code> as being the row with the highest average.</p>