title: Standardization of an numpy array
body: <p>I am trying to standardize a numpy array of shape(M, N) so that its column mean is 0. I think I have used the formula of standardization correctly where x is the random variable and z is the standardized version of x.</p>
  
  <blockquote>
    <p>z = (x - mean(x)) / std(x)</p>
  </blockquote>
  
  <p>But the column mean of the resulted array is not 0. They are very small number but not zero. Any insight regarding my misunderstanding or mistake is welcome. Here is my code:</p>
  
  <pre><code>import numpy as np
  
  X = np.load('data/filename.npy').astype('float')
  XNormed = (X - np.mean(X, axis=0))/np.std(X, axis=0)
  column_mean = np.mean(XNormed, axis=0)
  print(column_mean)
  </code></pre>