title: Numpy array indexing with two dimensions
body: <p>I have one numpy array with two dimensions, for the example let's say :</p>
  
  <pre><code>a = np.array([[1,2,3,4,5],[4,6,5,8,9]])
  </code></pre>
  
  <p>I tried to do <code>a = a[a[0]&gt;2]</code> but i got an error. I would like to obtain:</p>
  
  <pre><code> array([[3, 4, 5],
     [5, 8, 9]])
  </code></pre>
  
  <p>Is it possible ? thanks !</p>