title: Contour graph in python
body: <p>How would I make a countour grid in python using <code>matplotlib.pyplot</code>, where the grid is one colour where the <code>z</code> variable is below zero and another when <code>z</code> is equal to or larger than zero? I'm not very familiar with <code>matplotlib</code> so if anyone can give me a simple way of doing this, that would be great.</p>
  
  <p>So far I have:</p>
  
  <pre><code>x= np.arange(0,361)
  y= np.arange(0,91)
  
  X,Y = np.meshgrid(x,y)
  
  area = funcarea(L,D,H,W,X,Y) #L,D,H and W are all constants defined elsewhere.
  
  plt.figure()
  plt.contourf(X,Y,area)
  plt.show()
  </code></pre>