title: how to change the shape of a contour in matplotlib
body: <p>I am using <code>contour</code> or <code>contourf</code> in <code>matplotlib</code></p>
  
  <p>And the data is a 2D array with values in, like this:</p>
  
  <pre><code>1 2 3 3 3
  2 3 3 4 1
  2 3 4 5 6
  ...
  </code></pre>
  
  <p>The result I got is as below.
  <img src="https://i.stack.imgur.com/AqHZv.png" alt="enter image description here"></p>
  
  <p>It is like a square, while actually, the y extent is 600+ and x extent is only 350.
  So the figure should look like a rectangle, not a square.</p>
  
  <p>But I looked into the arguments in <code>contour</code> and <code>contourf</code>, there is no argument about changing the shape of the contour, or changing the length of the axis.</p>
  
  <p>for Adobe, here is the simplified code of my case:</p>
  
  <p>import matplotlib.pyplot as plt</p>
  
  <pre><code>m = [[1,2,3,4],
  [2,3,4,5],
  [2,2,1,5]]
  
  print m
  plt.contourf(m)
  plt.show()
  </code></pre>
  
  <p>Then, in this situation, how to use ax.axis()?</p>