title: How can I divide single values of a dataframe by monthly averages?
body: <p>I have the following 15 minute data as a <code>dataframe</code> for 3 years. With the first two columns being the index.</p>
  
  <pre><code>2014-01-01 00:15:00  1269.6      
  2014-01-01 00:30:00  1161.6      
  2014-01-01 00:45:00  1466.4      
  2014-01-01 01:00:00  1365.6      
  2014-01-01 01:15:00  1362.6      
  2014-01-01 01:30:00  1064.0      
  2014-01-01 01:45:00  1171.2      
  2014-01-01 02:00:00  1171.0      
  2014-01-01 02:15:00  1330.4      
  2014-01-01 02:30:00  1309.6      
  2014-01-01 02:45:00  1308.4      
  2014-01-01 03:00:00  1494.0    
  </code></pre>
  
  <p>I have used <code>resample</code> to get a second series with monthly averages.</p>
  
  <pre><code>data_Monthly = data.resample('1M', how='mean')
  </code></pre>
  
  <p>How can I divide the values in the last column by their monthly average with the result being still a time series on 15 minute granularity?</p>