sum a column depending on another column

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James Gooding
James Gooding 2012-8-2
Hi there,
I would like to sum values in a column where a criterion has been met in another column in a corresponding row of a matrix.
take the matrix:
xx 6 xx 1;
xx 9 xx 0;
xx 10 xx 1;
I want to sum the second column but only for rows where the fourth column is equal to one.
Hence, using the example, I would hope to have a solution of 16.
Any help with this simple problem is greatly appreciated.
James

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2012-8-2
out = sum(A(A(:,4)~=0,2))

更多回答（1 个）

Conrad
Conrad 2012-8-2
Something like this:
% Dummy data.
A =[ NaN 6 NaN 1;...
NaN 9 NaN 0;...
NaN 10 NaN 1];
idx = A(:,4)==1;
s = sum(A(idx,2));

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