how to sum specific matrix elements?

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!!!

Answer 1

[Image Analyst]

Try this:

rowsToSum = A(:, 2) < 0;
theSum = sum(A(rowsToSum, 1)); % Sum first column where second column is negative.

[anil hamzacebi]

It works exactly the way i need. Thank you for your help.

Answer 2

[VBBV]

%true
Total=sum(A(A(:,2)<0))

[anil hamzacebi]

it also works. thank you too :)