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selecting indices in a matrix and setting the rest to zero

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bsriv
bsriv 2023-3-14
评论： bsriv 2023-3-15
Hi,
I have a 414x22 matrix A and an array of indices
idx=[99 93 149 150 152 96 97 139 94 135 137 136 138 305 299 329 330 258 302 303 319 300 315 317 316 318]'
I would like to have all values in the matrix other than those in the rows of the indices (across columns) set to zero but I'm stuck on the code. It should be something like
new_idx=ismember(1:numel(A),idx)
A(~new_idx)=0
However that obviously treats the matrix as an array so only the first column had the numbers...

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采纳的回答

Torsten
Torsten 2023-3-14
A = rand(5,3);
idx = [2 4].';
idx_left = setdiff(1:size(A,1),idx)
A(idx_left,:) = zeros(numel(idx_left),size(A,2))

更多回答（1 个）

Walter Roberson
Walter Roberson 2023-3-14
new_A = zeros(size(A), 'like', A);
new_A(idx,:) = A(idx,:);

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