title: Taking away from numpy ndarray from another
body: <p>I have two <code>numpy.ndarrays</code> which one is a random sample from the other. I wish to take the smaller one (random sample) and remove those data points from the larger one.</p>
  <p>What is the code to do so?</p>
  <ul>
  <li>delete and remove do not work on ndarrays</li>
  </ul>
  <p>Thank you</p>