title: How to disregard the NaN data point in numpy array and generate the normalized data in Python?
body: <p>Say I have a numpy array that has some float('nan'), I don't want to impute those data now and I want to first normalize those and keep the NaN data at the original space, is there any way I can do that?</p>
  
  <p>Previously I used <code>normalize</code> function in <code>sklearn.Preprocessing</code>, but that function seems can't take any NaN contained array as input.</p>