Looking for the best way to calculate inflation

[PGerke]

I am working on a project where a forecast is calculated via a data action, this forecast value should now be part of the planning. The planning looks like this, for example:

I have a value on an account "Acc_1", this value is on the source "Forecast". Now I want to enter a value on the same account "Acc_1", but this value should be on source "Adjustment". A % value is entered on
 the account "Acc_2", this is on the source "Inflation". 

I want to write a DataAction that calculates the following:

Acc_1(Forecast) = Acc_1(Forecast) + (Acc_1(Forecast) * Acc_2(Inflation)) + Acc_1(Adjustment).

Or would it be a better way to create new accounts that have the respective ending like "_inflation".
Without including the Source?

One consideration was to create new accounts and work with account formulas. To do this, I would have created new accounts, provided them with the extension _x and written the formula in Acc_1_Forecast that calculates everything. But since a data action is supposed to calculate Acc_1_Forecast, I can't write a formula here.

So I'm looking for the best way to solve this problem.

[N1kh1l]

@PGerke 

I think the first approach is much cleaner in case you get inflation affecting more accounts. In second approach you will end up creating too many accounts. Having that extra source dimension will give you flexibility to model other requirements also. Just 2 thoughts on this approach, You could just use a single account say Acc1 to store all data and use source members Fcst/Inflation/Adjustment to store the different values. Also I would suggest that you store the final result post inflation in another source member for cleaner auditability of results else post inflation effect you will never be able to trace back original forecast value and if you run the calculation multiple times you will end up applying 5 % inflation on each run. Also you could separate the inflation % input and the inflation amount 50 on a different source. It will really help in Data reconciliation when you are analyzing this calculation at a later stage for multiple period and other combination.

Something like below.

MEMBERSET [D/ACCOUNT]="acc1"

MEMBERSET[D/SOURCE]=("FCST","ADJ","INF_INP","INF","FINAL_FSCT")

DATA(D/SOURCE]="INF')=RESULTLOOKUP(D/SOURCE]="INF_INP")*RESULTLOOKUP(D/SOURCE]="FCST")

DATA(D/SOURCE]="FINAL_FSCT')=RESULTLOOKUP(D/SOURCE]="FSCT")+RESULTLOOKUP(D/SOURCE]="INF")-RESULTLOOKUP(D/SOURCE]="ADJ")

Hope this helps !!

Nikhil