title: Calculate z-score in data bunch but excluding N.A
body: <p>So I got this bunch of data with N.A. values in them:</p>
  
  <p><a href="http://i.stack.imgur.com/XVlKo.jpg" rel="nofollow">Data Dump</a></p>
  
  <p>So how do I get the z-score of each column while excluding the N.A. values? Such that the z-score output looks like this?</p>
  
  <p><a href="http://i.stack.imgur.com/S5XiW.jpg" rel="nofollow">Z-Score value output</a></p>
  
  <p>So for this is what I have, which is based on previous questions:</p>
  
  <pre><code>cols = list(df.columns)
  df[cols]
  for col in cols:
      col_zscore = col + '_zscore'
      df[col_zscore] = (df[col] - df[col].mean())/df[col].std(ddof="N.A.")
  </code></pre>
  
  <p>but I got TypeError. </p>
  
  <p>Please help, I am really a beginner at this.</p>