title: Numpy inverse mask
body: <p>I want to inverse the true/false value in my numpy masked array.</p>
  
  <p>So in the example below i don't want to mask out the second value in the data array, I want to mask out the first and third value. </p>
  
  <p>Below is just an example. My masked array is created by a longer process than runs before. So I can not change the mask array itself. Is there another way to inverse the values?</p>
  
  <pre><code>import numpy
  data = numpy.array([[ 1, 2, 5 ]])
  mask = numpy.array([[0,1,0]])
  
  numpy.ma.masked_array(data, mask)
  </code></pre>