@PRIOR function question

Question

hi all, please explain me use of @prior(member, offset, range list) function
as I understand here:
member - a single member we want to return value of
offset - number of periods/some_members of range list
range list - members for offset choose
says, we have accounts
acc0
acc1
acc2
how should I define formula with @PRIOR function if I want calculate:
1) acc2=acc1 of previous N months, where N is stored in acc0
2) acc2=acc2 of previous N months, where N is stored in acc2 in custom_member2 of custom_dimension2

Answer 1

Hi,
Your question is a little hard to understand, so I will try to help by posting some information about the @PRIOR function and hoping it gets you moving.
It's important to remember that @PRIOR returns a numeric value. It's not a memberset function used to navigate the hierarchy. It's a function used to select one value from a set of values.
Typically, you just use it to step one month back in time and get the value of some account for use in the current month, like this:
"BegBalance" = @PRIOR("EndBalance");
What you don't see here is that this is taking advantage of the default values for the second and third arguments (the number of steps to go back, and the memberset to walk back through). The defaults are 1, and the-level-0-members-of-your-time-dimension.
Because I hate duplicating code in multiple fixes, specifying years in IF statements, and year-end maintenance, I tend to do something like this...
IF (@ISMBR("Jan"))
"BegBalance" = @PRIOR("EndBalance"->"Dec", 1, @LEVMBRS("Year", 0)); /*Note that you can cross-dim in the first argument*/
ELSE
"BegBalance" = @PRIOR("EndBalance");
ENDIF;
This is a good way to fix up code you inherit from consultants who only have to make things work in dev, don't mind nesting IF's and doing a bunch of double cross-dims to get from Jan to Dec, and are going to be long gone by the time the year rolls over. I'm sorry... have I gone off-topic?
The point is that you can use @PRIOR to pull numbers from elsewhere in the database, if you know what memberset you need to walk back through and how far back you need to walk. I presume you can use your acct0 as the second argument, since it's numeric, but you'll have to test that to see. You can also walk forward with @NEXT, if that helps you any.
Hoping you can find an answer in there somewhere,
-- Joe