Replacing same rows with same variables in first to third column

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Hi. I have two matrices named aa and m.
aa=[1 2 3 7
4 5 6 8
7 8 9 9
3 2 3 8
6 5 6 7
7 8 7 9];
mm=[1 2 3 5
4 5 6 9
7 8 9 6];
I want to replace the rows of aa with the rows of m that have the same values in first to third column.
How can I do that?
Thanks a lot.
  2 Comments
mr mo
mr mo on 21 Dec 2017
In my case there are only one same rows in ‘aa’ and ‘mm’

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Answers (2)

Jos (10584)
Jos (10584) on 21 Dec 2017
No need for loops at all! Use both outputs of ismember and replace accordingly
aa = [1 2 3 7
4 5 6 8
7 8 9 9
3 2 3 8
6 5 6 7
7 8 7 9
1 2 3 999];
mm = [1 2 3 5
4 5 6 9
7 8 9 6];
[tf,loc] = ismember(aa(:,1:3),mm(:,1:3),'rows')
% tf indicates which rows in aa are found where (loc) in mm (only for columns 1-3)
aa(tf,:) = mm(loc(tf),:) % replace those rows

KSSV
KSSV on 21 Dec 2017
Edited: KSSV on 21 Dec 2017
aa(1:3,1:3) = mm(1:3,1:3) ;

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