title: Find the row which has the maximum difference between two columns
body: <p>I have a DataFrame with columns <code>Gold</code> and <code>Gold.1</code>. I want to find the row where the difference of these two columns is the maximum.</p>
  
  <p>For the following DataFrame, this should return me row 6.</p>
  
  <pre><code>df
  Out: 
     Gold  Gold.1
  0     2       1
  1     1       4
  2     6       9
  3     4       4
  4     4       8
  5     5       5
  6     5       2 ---&gt; The difference is maximum (3)
  7     5       9
  8     5       3
  9     5       6
  </code></pre>
  
  <p>I tried using the following:</p>
  
  <pre><code>df.where(max(df['Gold']-df['Gold.1']))
  </code></pre>
  
  <p>However that raised a ValueError:</p>
  
  <pre>
  df.where(max(df['Gold']-df['Gold.1']))
  Traceback (most recent call last):
  
    File "", line 1, in 
      df.where(max(df['Gold']-df['Gold.1']))
  
    File "../python3.5/site-packages/pandas/core/generic.py", line 5195, in where
      raise_on_error)
  
    File "../python3.5/site-packages/pandas/core/generic.py", line 4936, in _where
      raise ValueError('Array conditional must be same shape as '
  
  ValueError: Array conditional must be same shape as self
  </pre>
  
  <p>How can I find the row that satisfies this condition?</p>