Summing output of for loop.
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I have a for loop producing an n x m matrix E fr every time the for loop runs. But i then need to sum all the output matrices from the for loop. Can anyone suggest how to do this. -I dont need to save the individual matrices, just the sum of them. Thanks
1 个评论
Jan
2012-4-30
What have you tried and which problem has occurred? Actually the procedure is trivial: Create the new matrix in each iteration and sum it up.
回答（1 个）
Geoff
2012-4-30
I gather you have the following situation, or something similar.
nloops = 100;
sumE = zeros(n,m);
for i = 1:nloops
% This loop generates a new E
E = [];
for j = 1:n*m
% magic goes here
end
% Now you want to sum E
sumE = sumE + E;
end
Well, the answer is contained above. =)
5 个评论
Jan
2012-4-30
Instead of "E=[]" a proper pre-allocation is recommended: "E=zeros(n, m)".
Dougie
2012-4-30
Geoff
2012-5-1
Yes, you stated that you already had a loop to compute E, so I slapped in a magical loop to compute E as a placeholder. And yes, as per Jan Simon's reminder, I would usually preallocate the array instead of declare it empty.
Jan
2012-5-2
@Dougie: If you had posted the relevant part of your program, Geoff wouldn't has to guess the part for calculating E.
Beside the tiny detail of the pre-allocation, Geoff's solution seems to be optimal. +1
Tilkesh
2017-4-14
Yes really it is magic
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