MATLAB: Aggregating numbers based on first column index

Question

Hi

I have a matrix as follows

x=[1 3;
   1 4;
   1 6;
   2 5;
   2 7;
   3 4;
   3 11;
   3 1;
   3 2]

I want to write a code or a loop that aggregates the numbers in the second column for each different number in the first column.

The result should be

y= [1 13;
    2 12;
    3 18]

Answer 1

[unique_keys, ~, uq_idx] = unique(x(:,1));
totaled_data = accumarray(uq_idx, x(:,2));
y = [unique_keys, totaled_data];