MATLAB: Adding matrices rows having the same id

matrix

Hello, I would like to sum rows of two matrices if they have the sam id (first column). For instance, I have a matrix A and matrix B:
A = [
1 4 5 6;
2 5 5 3;
3 9 8 2];
B = [
4 5 6 2;
2 9 4 1;
1 5 7 9;
3 5 6 7;
1 4 5 3];
I would like to get matrix C such that it looks at the first column and add the other columns if id is the same in both matrices.
C = [
1 13 17 18;
2 14 9 4;
3 14 14 9;
4 5 6 2];
Thank you

Best Answer

Assuming A and B have the same number of columns, 
AB = [A;B]; 
C = [unique(AB(:,1)), splitapply(@(x) sum(x,1), AB(:,2:end), AB(:,1))];
Result:
C =
     1    13    17    18
     2    14     9     4
     3    14    14     9
     4     5     6     2
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