title: How to delete columns in numpy.array
body: <p>I would like to delete selected columns in a numpy.array . This is what I do:</p>
  
  <pre><code>n [397]: a = array([[ NaN,   2.,   3., NaN],
     .....:        [  1.,   2.,   3., 9]])
  
  In [398]: print a
  [[ NaN   2.   3.  NaN]
   [  1.   2.   3.   9.]]
  
  In [399]: z = any(isnan(a), axis=0)
  
  In [400]: print z
  [ True False False  True]
  
  In [401]: delete(a, z, axis = 1)
  Out[401]:
   array([[  3.,  NaN],
         [  3.,   9.]])
  </code></pre>
  
  <p>In this example my goal is to delete all the columns that contain NaN's. I expect the last command 
  to result in:</p>
  
  <pre><code>array([[2., 3.],
         [2., 3.]])
  </code></pre>
  
  <p>How can I do that?</p>