# MATLAB: Sum of rows with whose row numbers are specified by another array

TTX =    20     9     2     7    40    10    10     1    60     2    10     9     0    10     5    10    40     7     9     7    40     1     2     8     0     3     5     8    60     6    10     4    20    10     8     7     0    10    10     2
>> TTX = [...    20     9     2     7    40    10    10     1    60     2    10     9     0    10     5    10    40     7     9     7    40     1     2     8     0     3     5     8    60     6    10     4    20    10     8     7     0    10    10     2];>> [U,~,X] = unique(TTX(:,1));>> Y = splitapply(@(x)sum(x,1),TTX(:,2:4),X);>> M = [U,Y]M =     0    23    20    20    20    19    10    14    40    18    21    16    60     8    20    13