how to sum specific matrix elements?

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anil hamzacebi
anil hamzacebi 2020-12-20
评论： anil hamzacebi 2020-12-20
Hello everyone,
i have a 10x2 matrix. i want to sum all the elements in the first column while the second column has the negative values. for the example matrix below,
i want a b matrix that gives me 2+4+4 result. (2,4 and 4 are the first column numbers which has negative numbers in the second column)
A=[2 -3;4 -4;5 3;4 -2;5 4;1 3];
I hope you can help me, thank you all!!!

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采纳的回答

Image Analyst
Image Analyst 2020-12-20
Try this:
rowsToSum = A(:, 2) < 0;
theSum = sum(A(rowsToSum, 1)); % Sum first column where second column is negative.

更多回答（1 个）

VBBV
VBBV 2020-12-20
编辑：VBBV 2020-12-20
%true
Total=sum(A(A(:,2)<0))

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