title: How could I remove the rows of an array if one of the elements of the row does not satisfy a condition?
body: <p>I would like to remove the rows of an array when the elements of third column of the array are less than specific amount. For example:</p>
  
  <pre><code>a=np.array([[2331.13,1944.88,23.1379,7,3.18339,0.482105],
  [8168.44,1904.70,19.5025,265,4.12642,0.0376510],
  [7389.36,1983.97,14.3581,3937,6.04109,0.713416],
  [1765.18,1944.29,22.5495,35,2.30717,0.794432],
  [2319.33,1946.68,22.4300,25,3.63676,0.0210690],
  [785.666,2090.69,14.7940,1095,2.52823,0.999842],
  [4071.24,2186.92,22.6616,31,2.79309,0.0312501],
  [7082.51,2191.69,23.0122,19,2.53166,0.687001]])
  </code></pre>
  
  <p>I would like to remove rows which satisfy the following condition:</p>
  
  <pre><code>a[:,2]&lt;15.0
  </code></pre>
  
  <p>Cheers.</p>