title: How to get Quarter wise sales column in pandas
body: <p>My data frame is below</p>
  
  <p>sales[['Month','Sales2015','Sales2016']]</p>
  
  <pre><code>Month   Sales2015   Sales2016
  0   Aug 0.00    13208.52
  1   Oct 10500.78    23114.91
  2   Jun 0.00    6627.00
  3   Mar 19881.00    13254.00
  </code></pre>
  
  <ul>
  <li>How to get Quarter wise sales in 2015 and 2016</li>
  </ul>
  
  <p>Approach is Create Qtr using Q1,Q2,Q3,Q4 using numpy.where() </p>
  
  <p>Expected oUt</p>
  
  <pre><code>Qtr  2015                                2016
  Q1  sum(Jan2015 + Feb2015 + Mar2015) 
  Q2  sum(Apr2015 + May2015 + Jun2015) 
  Q3  sum(Jul2015 + Aug2015 + Sep2015) 
  Q4  sum(Oct2015 + Nov2015 + Dec2015) 
  </code></pre>
  
  <p>Since its not date (2011-10-01) i cant use <code>pd.to_datetime(sales_qtr.Month).dt.quarter</code></p>