That is exactly what I need! Thank you for helping me on that.
The last step would be to have slopes averages on a per-month basis or any variable controlled via columns, much like your “average” column.
=Attendance_All.filter(Month(Date)=Month(thisRow.Date)).Count()
Works correctly, returning the correct # of rows for the month. When I add:
=Round(Attendance_All.filter(Month(Date)=Month(thisRow.Date)).Count().Average())
It becomes invalid. Any guesses?