title: Derive Month to Date (MTD) from Year to Date (YTD) numbers in Pandas
body: <p>I have the below table with YTD numbers, every month (cumulative). I need to derive MTD numbers by deducting the prior month numbers from the later month numbers. Every month the numbers keep on adding. January numbers should remain the same becoz MTD and YTD numbers are same for Jan.Thanks for your help.</p>
  
  <p><a href="https://i.stack.imgur.com/dL0kO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dL0kO.png" alt="df1"></a></p>
  
  <p>Expected Result:</p>
  
  <p><a href="https://i.stack.imgur.com/NiNBu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NiNBu.png" alt="df2"></a></p>