title: Normalizing the columns of a dataframe
body: <p>I want to normalize the column in the following dataframe:</p>
  
  <pre><code>import pandas as pd
  from pprint import pprint
  d = {'A': [1,0,3,0], 'B':[2,0,1,0], 'C':[0,0,8,0], 'D':[1,0,0,1]}
  df = pd.DataFrame(data=d)
  df = (df - df.mean())/df.std()
  </code></pre>
  
  <p>I am not sure if the normalization is done <em>row-wise</em> or <em>column-wise</em>.</p>
  
  <p>I intend to do <code>(x - mean of elements in the column)/ standard deviation</code>, for each column.</p>
  
  <p>Is it required to divide the standard deviation by number of entries in each column?</p>