Array.aggregate()
Array.aggregate (Columns,Function, Params)
Aggregates rows by unique values in column 1, with given function to columns with the parameters specified.
IM(4)
.fillwith(1..4) .aggregate(3,SUM)
gives
1 16
Total of column 3 for each row where first row has a unique value, which in this case is 1.
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4