Total Distinct Ever but for each successive month

[#1]

ok here's one

I have a chart (month as dimension) that I'd like to display an active rate. Active rate would be calculated as the distinct count of users for that month divided by the total that had ever been seen for that month and prior months. I can determine how many users there ever where, but how to count the total users up to a point in time.

For example:
                 Active Users                  Total Users Ever                Active Rate

Jan           1,000                              1,000                                  1.0

Feb           900                                 1,200                                  .75

Mar           500                                 1500                                   .30

So looking to perform the calculation that detemined total users ever but for each successive month and then chart the active rate.

I can get the total users ever for the last month, but how would I get it for Feb and Jan? Seems to be like a YTD but cant wrap my ahead around it conceptually.

[#2]

Hi,

As per my understanding if, Active Users and total users are 2 expression, so you can add the third expression as exp1/exp2  to achieve your result row wise for the 3rd.

[#3]

Actually, I'm looking for help to get expression #2, which is the total users ever, but according to that month.