# Subtracting a value in a 3D array with all values in another 3D array

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Sarah Bassiouny on 26 Nov 2022
Commented: Jan on 27 Nov 2022
Hello, I have 2 three-dimensional arrays, i would like to take the first value in the first array and subtract it with all values in the second array, and then the second value in the first array with all values in the second array, and in each time the smallest value of the subtraction is put in a new array.
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Sarah Bassiouny on 26 Nov 2022
min(abs(x-y))

Jan on 26 Nov 2022
Edited: Jan on 26 Nov 2022
A = rand(5,6,7);
B = rand(6,7,8);
D = min(A(:).' - B(:), [], 1);
Result = reshape(D, size(A));
If the intermediate matrix A(:).'-B(:) exhausts the available RAM, use a loop:
Result = zeros(size(A));
for k = 1:numel(A)
Result(k) = min(A(k) - B, [], 'all');
end
##### 2 CommentsShowHide 1 older comment
Jan on 27 Nov 2022
[D, Pos] = min(A(:).' - B(:), [], 1);
determines the position also as linear index. But what do you exactly need as output "position" for 3D arrays?
I do not understand, what this means: "if the smallest value is in position 4 then the value in the results matrix is the difference, and the array is 6." Why 6?