title: Convert a numpy array of strings to a numpy matrix
body: <p>So I have a numpy array of strings that contain numeric values separated by spaces, for example:</p>
  
  <pre><code>np.array(['1 2', '3 4'])
  array(['1 2', '3 4'], dtype='&lt;U3')
  </code></pre>
  
  <p>and I want to convert it to a numerical matrix like:</p>
  
  <pre><code>np.array([[1,2],[3,4]])
  array([[1, 2],[3, 4]])
  </code></pre>
  
  <p>I'm looking for an operation that can leverage numpy vecotrized operations, as speed is important here. The rows have length 2 in this example, but I need a general approach with an arbitrary row length.</p>
  
  <p>Thanks!</p>