Converting empty date fields to the filtered month

Hi Team,

I am very new to PBI so I would appreciate any suggestion!

What am I trying to calculate: % of users who enrolled into a learning activity vs all headcount, both monthly and YTD. I got PBI to calculate the number of users, but I don't know how to turn it into %. I have included picture of how this looked in an old PowerPoint/Excel report, and dummy data with the tab of how we would do the calculations manually.

What I have as a source: A data table that lists all learning activities with users and learning date, and includes also the list of users who didn't participate and their date is (blank) - see dummy data.

What I want to know: Is there a formula I can use that will allow the inactive users to be always displayed on the chart, for any month I choose? 

• Currently, the YTD works. But if I filter for month, the inactive users disappear, because their month is (blank) (see attached image)
• Ideally, I would want that each time I filter for month, I get a visual showing me the difference between active and inactive users for the selected month.

I have looked at this solution, but it replaces the empty field with current date, and I am too green to edit it myself. Thank you in advance for any suggestions!

Old reporting in PPT - % of headcount displayedInactive users disappear when date is selected