Power BI measure to calculate students retained between study periods - powerbi

Question

Just started getting into Power BI/DAX after living in Excel for most of my life.
I'm working on a retention/attrition rate report and I am stuck on how to compare one pool of students in one study period to another pool in another study period.
The calculation is relatively simple:
(Returned Students in Study Period X+1) / (Enrolled students in Study Period X - Graduated Students in Study Period X)
So if I had 110 students enrolled in 201902, and 10 graduated, and 10 did not return in 201903, I would have a 90% retention rate:
(90 Returned Students in 201903) / (110 Enrolled Students in 201902 - 10 Graduated Students in 201902)
= 90 / (110 - 10)
= 90 returned / 100 eligible
Ideally, since not all study periods follow the same naming convention in the larger data set (it varies by institution), the calculation would be based on the 'Study Period Order' as those will be sequential regardless of 'Study Period/RPL' code.
Sample data here: Sample File
Thank you for any guidance you might be able to provide.

Answer 1

It depends on what you add to the visualization. If we add [Study Period Order] to visualization, then your calculation may look like:
calc =
var __StudentsCurrentSeasson =
CALCULATE (
COUNT ( 'YourTable'[Student Code] ),
FILTER (
VALUES ( 'YourTable'[Study Period Order] ),
[Study Period Order] = SELECTEDVALUE ( [Study Period Order] )
)
)
var __StudentsGraduatedCurrentSeasson =
CALCULATE (
COUNT ( 'YourTable'[Student Code] ),
FILTER (
VALUES ( 'YourTable'[Study Period Order], 'YourTable'[Status] ),
[Study Period Order] = SELECTEDVALUE ( [Study Period Order] ) && 'YourTable'[Status] = "Graduated"
)
)
var __StudentsLastSeasson =
CALCULATE (
COUNT ( 'YourTable'[Student Code] ),
FILTER (
VALUES ( 'YourTable'[Study Period Order] ),
[Study Period Order] = SELECTEDVALUE ( [Study Period Order] ) - 1
)
)
return DIVIDE(__StudentsCurrentSeasson, (__StudentsLastSeasson - __StudentsGraduatedCurrentSeasson ) )
If you have multiple StudentCode in one Period then use distinctcount instead of count.