title: How to remove all rows in a numpy.ndarray that contain non-numeric values
body: <p>Basically, I'm doing some data analysis.  I read in a dataset as a numpy.ndarray and some of the values are missing (either by just not being there, being <code>NaN</code>, or by being a string written "<code>NA</code>").</p>
  
  <p>I want to clean out all rows containing any entry like this.  How do I do that with a numpy ndarray?</p>