How to sum pages of a multidimensional array inside a structure array?

Hi,

I have a structure array "A" with one field "a". The field "a" consists from 200 muldidimensional arrays of equal size 11x11x5. let's call the elements within field "a" in the following way: "a1", "a2", "a3" and so on up to "a200". For element "a1" I have to sum all pages from 1 to 5 and at the end I should have a matrix 11x11. The same summation I should do for every element within the field "a" from element "a1" to element "a200". At the end I should get a struct array "A" with field "a". Field "a" will now have 200 elements "a1" to "a200" and these all will be matrices 11x11.

I have tried to do the sum in this way

for p = 1:200
A(p).a_sum = sum(structfun(@sum, A(p).a(:,:,3)));
end

But I get this error: Error using structfun Inputs to STRUCTFUN must be scalar structures.

Can you help me how to write the sum in a proper way?

Thanks!

Answer 1

[Jan]

"A(p).a(:,:,3)" is a matrix, therefore you cannot provide it as input to structfun. You could use structfun for the summation:

structfun(@x sum(x, 3), A)

but this is easier and most likely faster:

for p = 1:200
  A(p).a_sum = sum(A(p).a, 3);
end

[EB]

The easier approach works fine.

Thanks!

Answer 2

[Jos (10584)]

Given the description, I assume you have an array of structures A. Each element of this array has a field a which holds a 3D (11x11x5) array. For each of the the 200 elements of the structure array A you want to sum this field across the 3rd dimension:

% create some data
% 10 element structure array "A" with a field "a" holding a random 3x3x2 array
[A(1:10).a] = deal(rand(3,3,2))   % smaller examples work better

myfun = @(k) sum(A(k).a, 3)   % a function to sum across the 3d dimension of field a
C = arrayfun(myfun, 1:numel(A), 'un', 0)   % apply myfun to all elements of A
[B(1:numel(A)).a_sum] = deal(C{:})   % distribute over elements of a new structure array