Summing arrays within a cell array.

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mathman
mathman 2018-1-4
评论： Jan 2018-1-7
I've got a cell array which consists of 501 4D arrays, I want to sum all of these together and output a single 4D array. I've tried using sum and plus but get the error saying too many input arguments.
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Jan
Jan 2018-1-4
Please post the code, instead of telling what it should do, and a copy of the complete error message, instead of a short rephrasing. Thanks.

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Jan
Jan 2018-1-4
编辑：Jan 2018-1-4
What about a simple loop?
S = 0;
for k = 1:numel(C)
S = S + C{k};
end
You can check if a vectorized code is faster:
S = sum(cat(5, C{:}), 5);
While it does not have the overhead for the loop, it requires a large temporary array.
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mathman
mathman 2018-1-6
Sorry, I just want to make sure I'm understanding the loop correctly. So S would initially be 0. It would then be added to the first cell array C{1}. This would change the value of S to equal to C{1} which would then be added to C{2} and so on?
Jan
Jan 2018-1-7
@mathman: Only the variable on the left side of the assignment operator "=" is modified. This means, that S is 0 initially. Then in the first iteration, S is replaced by S + C{1}. In the 2nd iteration, this new S is replaced by S + C{2}, and so on. This is equivalent to (assuming that C has 5 elements):
S = C{1} + C{2} + C{3} + C{4} + C{5}
You can simply try if:
C = {1,3,4,7,8}
S = 0;
for k = 1:numel(C)
fprintf('Loop %d\n', k);
disp(C{k})
disp(S)
S = S + C{k};
disp(C{k})
disp(S)
end
The debugger helps also to find out, what's going on: https://www.mathworks.com/help/matlab/matlab_prog/debugging-process-and-features.html

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