title: creating daily price change for a product on a pandas dataframe
body: <p>I am working on a data set with the following columns:</p>
  
  <p>order_id</p>
  
  <p>order_item_id</p>
  
  <p>product mrp</p>
  
  <p>units</p>
  
  <p>sale_date</p>
  
  <p>I want to create a new column which shows how much the mrp changed from the last time this product was. This there a way I can do this with pandas data frame?</p>
  
  <p>Sorry if this question is very basic but I am pretty new to pandas.</p>
  
  <p>Sample data:
  <a href="https://i.stack.imgur.com/6xwRd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6xwRd.png" alt="enter image description here"></a></p>
  
  <p>expected data:</p>
  
  <p>For each row of the data I want to check the amount of price change for the last time the product was sold.</p>