Formula not working within set expression

[lostSquirrel112]

I have a dataset of how long customers of a certain segment were active with our company as follows...

Customer	AgeMonths
A	17
B	29
C	39
D	40
E	47
F	47
G	48
H	49

I'm trying to get the percentage  remaining  after each month, but I'm not even able to calculate the remaining customers in each month let alone the percentage of the total using the following formula in a chart...

"customers Remaining"

Count(DISTINCT TOTAL {<cohort={'2018-B_Group'}, AgeMonths = {">=$(=RowNo()-1)"}>} [Customer ID])

But my table just returns the total number of customers and disregards the age evaluation formula in the expression as seen below...

Starting in month 18 I would expect to see 7 customers since customer A drops off but instead it still shows 8.

How can I show the remaining customers by month? Even better would be to show the percentage of all 8 remaining in each month because I have multiple segments I want to graph against each other.

Any help that can be provided would be greatly appreciated.

[hic · Accepted solution]

Both set analysis and dollar expansions (the "$(=RowNo()-1)") are evaluated BEFORE the chart is expanded, resulting in one global value. So you cannot use this to create something that should be calculated row-by-row.

Take a look at the Above() function. This can be used to calculate something that is based on the above row.

[lostSquirrel112]

Thanks Henric, Above took care of it!