# Power BI | Date functions exercise | Showing cumulative percentage of previous year's sales

This exercise is provided to allow potential course delegates to choose the correct Wise Owl Microsoft training course, and may not be reproduced in whole or in part in any format without the prior written consent of Wise Owl.

You can learn how to do this exercise on the relevant Wise Owl classroom training course (sadly for the moment only in the UK).

 Software ==> Power BI  (92 exercises) Version ==> Latest update Topic ==> Date functions  (2 exercises) Level ==> Average difficulty
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help).

You need a minimum screen resolution of about 700 pixels width to see our exercises. This is because they contain diagrams and tables which would not be viewable easily on a mobile phone or small laptop. Please use a larger tablet, notebook or desktop computer, or change your screen resolution settings.

Create a new Power BI file, and load both tables from the workbook in the above folder:

The tables you'll need to load to do this exercise.

Create a relationship between the two tables by the date field in each, and set your calendar table up to work correctly.  You should now be able to produce a matrix like this:

You don't actually need to create this for the exercise, but it might give you the confidence you've set everything up correctly!

The ultimate aim of this exercise is to create the following table:

See below for lots of help on how to create these measures!  Note that you should filter your table to show only data for January 2019, otherwise you won't see these figures.

To do this, you'll need to create measures for the last 3 columns, using the guidance notes below:

Measure Notes
YearToDate Count the cumulative year-to-date number of purchases, using either the TOTALYTD function or the CALCULATE and DATESYTD functions combined.
PreviousMonth Use the CALCULATE function to count the number of purchases, with the PARALLELPERIOD function to change the filter context to the dates for the previous month.
CumulativeRatio Divide the first measure by the second!

Remember to filter your table to show only figures for January 2019.

Save this file as Last month, then close down the Power BI instance that you're using.

You can unzip this file to see the answers to this exercise, although please remember this is for your personal use only.