title: Pandas values substituted by numpy matrix?
body: <p>My question is very simple. I have a dataFrame and I want to add or substract my DataFrame by a numpy matrix.
  The size of the two matrix are identical.
  I would like this kind of things : <code>my_matrix.values = my_matrix.values + numpy_matrix</code>, or <code>my_matrix.values = my_matrix.values - numpy_matrix</code>, very efficiently.</p>
  
  <p>Is not possible? Because the size of ma matrix is quite huge and the "update", subtract or the "add" command is quite long. Is it better to recreate a DataFrame each time?</p>