Row/column-wise logical indexing
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I have a matrix
A=[1 2 3;
4 5 6;
7 8 9];
where each row represents a group of numbers. I have a logical matrix
L = [ 0 0 0 1 1 1 1 1 1;
1 1 1 0 0 0 1 1 1;
1 1 1 1 1 1 0 0 0]
where each column represents the groups of A I want to extract.
For example,
A(L(:,1),:) gives me
[4 5 6;
7 8 9]
A(L(:,4),:) gives me
[1 2 3;
7 8 9]
Is there a way to extract all such pairs of rows of A in one vectorized step instead of looping over the columns of L?
回答（1 个）
Akira Agata
2019-6-6
How about the following solution?
B = arrayfun(@(k) A(L(:,k),:), 1:size(L,2), 'UniformOutput', false);
Then, your can obtain cell array B where B{1} = A(L(:,1),:), B{2} = A(L(:,2),:), ... B{9} = A(L(:,9),:).
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2019-6-5
2019-6-6
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