Adding matrices rows having the same id

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Mo H 2020-3-22

评论： Adam Danz 2020-3-22

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

Mo H 2020-3-22

Adam provided a great answer, and I hope it is helpful for the community

Adam Danz 2020-3-22

Thanks for restoring the question and for the compliment, Mohammad.

Adam Danz 2020-3-22

编辑：Adam Danz 2020-3-22

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 =
  13    17    18
  14     9     4
  14    14     9
   5     6     2

Mo H 2020-3-22

thank you a lot

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