title: Plotting vector fields in python (matplotlib)
body: <p>I found this code on <a href="http://matplotlib.sourceforge.net/examples/pylab_examples/quiver_demo.html" rel="noreferrer">http://matplotlib.sourceforge.net/examples/pylab_examples/quiver_demo.html</a></p>
  
  <pre><code>from pylab import *
  from numpy import ma
  
  X,Y = meshgrid( arange(0,2*pi,.2),arange(0,2*pi,.2) )
  U = cos(X)
  V = sin(Y)
  
  #1
  figure()
  Q = quiver( U, V)
  qk = quiverkey(Q, 0.5, 0.92, 2, r'$2 \frac{m}{s}$', labelpos='W',
                 fontproperties={'weight': 'bold'})
  l,r,b,t = axis()
  dx, dy = r-l, t-b
  axis([l-0.05*dx, r+0.05*dx, b-0.05*dy, t+0.05*dy])
  
  title('Minimal arguments, no kwargs')
  </code></pre>
  
  <p>Now, how can I see this graphic? Better yet, how can I save it to a file as, let's, say, JPEG? The code seems to run but I can't see anything happening.</p>