For example, if
A = [7,8,1,1,2,2,2]; % the bins (or subscripts)
B = [2,1,1,1,1,1,2]; % the array
then the desired function "binsum" has two outputs, one is the bins, and the other is the sum. It is just adding values in B according to subscripts in A. For example, for 2, the sum is 1 + 1 + 2 = 4, for 1 it is 1 + 1 = 2.
[bins, sums] = binsum(A,B);
bins = [1,2,7,8]
sums = [2,4,2,1]
The elements in "bins" need not be ordered but must correspond to elements in "sums". This can surely be done by "for" iterations, but "for" iteration is not desired, because there is a performance concern. It is best if there is a build in function for this.
Thanks a lot!