MATLAB: Consolidating row values from previous column duplicate values.

summationunique multiple column values

Hi all,
Is it possible to write a script to make MATLAB look at the first two columns of a matrix, and if there are multiple rows where Column 1 and Column 2 have the same values, to put these rows together and sum the corresponding values of a third column.
An example would be like this;
[a  x  2;
a  x  3;
b  x  4;
a  y  5;
b  y  6;
b  y  7;
c  y  8]
and so the script will recognize there are two rows with a in column 1 and x in column 2, so it will put them together and add the values in the third row.
So the output would be like this;
[a  x  5;
b  x  4;
a  y  5;
b  y  13;
c  y  8]
Forgive my bad formatting of the matrix, but any help will be greatly appreciated!
Kind regards
Willem

Best Answer

You need the accumarray function:
A = [1 1 3;
     1 1 4;
     1 1 7;
     1 2 1;
     1 2 6;
     2 3 5;
     3 6 4; 
     3 6 9;
     3 6 3];
[Aunique,i,j] = unique(A(:,[1 2]),'rows');
Asum = accumarray(j,A(:,3),[],@sum);
output = [Aunique,Asum]
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