In Expression Builder, the AGO function has the following template:
Ago(<<Measure>>, <<Level>>, <<Number of Periods>>)
<<Measure>> represents the logical measure column from which you want to derive. In this example, you would select the measure "Dollars" from your existing logical fact tables.
<<Level>> is the optional time series grain you want to use. In this example, you would select "Quarter" from your time dimension.
<<Number of Periods>> is the size of the offset, measured in the grain you provided in the <<Level>> argument. For example, if the <<Level>> is Quarter and the <<Number of Periods>> is 2, the function displays dollars from two quarters ago.
Using this function template, you can create an expression for a One Quarter Ago measure, as follows:
Ago("Sales"."Base Measures"."Dollars" , "Sales"."Time MonthDim"."Quarter" , 1)
The <<Level>> parameter is optional. If you do not want to specify a time series grain in the AGO function, the function uses the query grain as the time series grain.
For example, you could define Dollars_Ago as Ago(Dollars, 1). Then, you could perform the following logical query:
SELECT Month, Dollars, Dollars_Ago
The result is the same as if you defined Dollars_Ago as Ago(Dollars, Month, 1). Alternatively, you could perform the following logical query:
SELECT Quarter, Dollars, Dollars_Ago
The result is the same as if you defined Dollars_Ago as Ago(Dollars, Quarter, 1).