title: How to calculate efficient local average of each coordinate of large matrix (average filter) in python
body: <p>I have large matrix, 4000x4000
  I need to calculate local average of 11x11 window for each x,y of this matrix
  Generally it must be something like</p>
  
  <pre><code>for x in range(4000)
    for y in range(4000)
      b[x,y]=mean(a[x-5:x+5,y-5:y+5]
  </code></pre>
  
  <p>But this will run a lot of time
  Is it some more efficient way to do this?
  Thanks. </p>