indexing and performing operations in matrix

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cgo
cgo 2015-11-11
评论： cgo 2015-11-11
I have an nx2 matrix A. I also have an interaction matrix of A, which looks like this:
interact = [1 2;
1 4;
1 5;
2 1;
2 3;
3 4;
3 6]
These numbers are just the index. I want to perform the following operation: (A(1,:) - A(2,:))+(A(1,:)-A(4,:))+ (A(1,:)-A(5,:)), then store result into some matrix R(1,:)
Likewise, A(2,:) - A(1,:) + A(2,:) - A(3,:) = R(2,:) etc.
How do I do this?
  2 个评论
Walter Roberson
Walter Roberson 2015-11-11
Could you confirm that all of the entries with the same value in column 1 should be treated as a group? And if that is the case, then what should happen if the entrees are not consecutive, such as if there was another entry beginning with 1 after the [3 6] ?
cgo
cgo 2015-11-11
I got it already!!!
for val=1:n
iv=interact(ismember(interact(:,1),val),2)
repmat(A(val,:),size(iv,1),1)
A(iv,:)
end
Thanks for your help though.

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