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how to extract rows and leave zeros behind?

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MAHMOUD ALZIOUD
MAHMOUD ALZIOUD 2017-11-11
评论： MAHMOUD ALZIOUD 2017-11-11
Dear All, I have a big matrix called A, I extract another matrix from this A and call it B based on a condition of the value x in the matrix A, I wrote this code but it doesnt work well, can any body please help fix it? I need to extract the new matrix B and leave the rows as zeros in the original matrix A.
B= A(x(:,1)>9.84 & x(:,1)<12.47 , :);
A(find(A(B,:)))=0;

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Walter Roberson
Walter Roberson 2017-11-11
B= A(x(:,1)>9.84 & x(:,1)<12.47 , :);
leaves B as a subset of A, having selected some of the rows but retaining all columns.
A(B,:)
then uses that subset as an index into A. That is mostly going to fail as the entries are probably not zero.
Try
mask = x(:,1)>9.84 & x(:,1)<12.47;
B = A(mask, :);
A(mask, :) = 0;
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MAHMOUD ALZIOUD
MAHMOUD ALZIOUD 2017-11-11
Ok Mr Walter I will give it a try, this looks very correct and simple. Thank you very much

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