Line chart accumulation gives strange results

[njimack]

Hi,

These 2 charts use identical data and expressions, the only difference is one uses the Accumulation modifier.  All amounts are positive yet the accumulated chart starts to reduce from July.

I've never seen behaviour like this before and I'm completely stumped.  Any assistance gratefully received!

[ibdK4evr]

Hi,

In the accumulated chart, is the data directly from the table coming as accumulated numbers or the month level numbers are being added up in the set expression. 

[njimack]

It's all monthly numbers.  Below is the table and the expression I'm using...

if(CYTDFlag=1,sum({<Version = {"Actual"},TM1_Account={"NII excl LP"}>}
(Amount)),
sum({<Version = {"Forecast"},TM1_Account={"NII excl LP"}>}
(Amount)))