You can think of Aggr() function as GROUP BY clause in a SQL query. This function doesn't return a single value, but an array of aggregated values grouped by one or more dimensions.
For example, if you use Sum(Aggr(Sum(Amount), Office)) on the following data:
| Office | Salesman | Amount |
| London | Albert | 1000 |
| London | Bob | 1500 |
| Paris | Carlos | 2000 |
| Paris | David | 2500 |
| Paris | Eric | 3000 |
Then:
- The Aggr(Sum(Amount), Office) part of the expression returns array [2500,7500] corresponding to [Sum(London), Sum(Paris)]
- Sum(Aggr(Sum(Amount), Office) ) = 2500 + 7500 = 10000
In this simple example, two expressions Sum(Amount) and Sum(Aggr(Sum(Amount), Office) ) return the same value. Sum(Aggr(Sum(...)) is usually used when you want to redefine the computation scope by using Set Analysis, If condition or TOTAL keyword in the inner and outer Sum() functions
For this example, another aggregation function such asMax(Aggr(Sum(Amount), Office) ) = Max(2500, 7500) = 7500 (i.e find max sales amount between the two offices) would make more sense.
You can read more about Aggr function at https://www.analyticsvidhya.com/blog/2014/02/aggr/
Hope this helps!
