How to extract matrix value given condition on another column
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So i have a matrix: [1 2 3 4; 5 6 7 8; 1 0 1 1]
The condition is that the third column must equal one. Then I take that corresponding row to extract the value from column 2.
So i need a code that extracts 5, 7, and 8 into a separate matrix.
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Answers (1)
Cam Salzberger
on 5 Sep 2017
Hello Jesutoyosi,
Based on your example matrix, I believe you meant that you want to extract from row 2 every value that is a 1 in row 3.
In that case, logical indexing is your best friend.
whichCols = oldMat(3,:) == 1;
newMat = oldMat(2,whichCols);
Or, because 1 is able to be converted to true, and 0 to false, you can just do this:
newMat = oldMat(2, logical(oldMat(3,:)));
-Cam
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