How to quickly assign the values of a matrix using a given array?
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Dear All,
I have an array A which contains two columns of integers. I want to build a matrix B in the following way.
For example,
A = [2 9; 1 5; 8 3]
The matrix B should be suilt as follows:
B = [0 1 0 0 0 0 0 0 -1 0; 1 0 0 0 -1 0 0 0 0 0; 0 0 -1 0 0 0 0 1 0 0]
How can I create matrix B for a goven A?
Thanks.
Benson
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DGM
le 23 Mai 2021
Modifié(e) : DGM
le 23 Mai 2021
Here is one way:
A = [2 9; 1 5; 8 3]
s = [size(A,1) 10]; % you're going to have to specify the output width
B = zeros(s);
B(sub2ind(s,(1:s(1)).',A(:,1))) = 1;
B(sub2ind(s,(1:s(1)).',A(:,2))) = -1;
B % show the result
2 commentaires
DGM
le 24 Mai 2021
I really have no familiarity with handling sparse matrices or how to optimize for them. I'm sure someone else can though.
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Walter Roberson
le 23 Mai 2021
S = 10;
A = [2 9; 1 5; 8 3]
(A(:,1) == (1:S))-(A(:,2) == (1:S))
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