title: Get mean value of certain part of array
body: <p>I have an array:</p>
  
  <pre><code>import numpy as np
  
  array = np.array([[ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
                    [ 1, 1, 4, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
                    [ 1, 0, 2, 22, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1],
                    [ 1, 0, 1, 34, 99, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1],
                    [ 1, 0, 5, 11, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1],
                    [ 1, 0, 6, -5, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1],
                    [ 1, 0, 88, 0, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1],
                    [ 1, 1, 333, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
                    [ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
                    [ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]])
  </code></pre>
  
  <p>I want to get the mean values of a certain part of my area. The areas center is at the index <code>[3][4]</code> and goes 5 steps to each direction. </p>
  
  <p>I thought one approach would be to create a sub array for the area of interested and use <code>numpy.mean</code> on that sub array. How could I create that sub array?</p>
  
  <p>Also I am interested in other approaches or ideas.</p>