Matrix Size Changing in a loop

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Burak 2017-3-26

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https://ww2.mathworks.cn/matlabcentral/answers/332046-matrix-size-changing-in-a-loop

评论： KSSV 2017-3-27

Hi, I need to calculate a matrix say A(v,n,m) like this code

for n=1:5
      m=-n:n;
   for v=1:5
    for i=1:numel(m)
         A(v,n,i)= % my function
      end 
    end
  end

now A is a 5x5x11 matrix, but I want to calculate A as a changing matrix size like for m=1 , A=10x10 for m=2 A=9x9, for m=3 A=8x8, same as for negative values of m. Because I need to inverse of A, and I can't inverse for all m values if I calculate like my code. How can I do that , I don't want to calculate it separately. Thanks for any help.

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Joshua 2017-3-27

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From what I understand, you want to create a 3D array which holds matrices of different sizes in the 3rd dimension. Then, you want to invert each of these matrices ignoring the extra zeros. I think I found a solution.

clear
clc
num=11;
m=-3:3;
for i=1:numel(m)
    for v=1:num-m(i)
        for n=1:num-m(i)
            A(v,n,i)= rand(1);
        end
    end
    Ai(1:num-m(i),1:num-m(i),i)=inv(A(1:num-m(i),1:num-m(i),i));
end

num is an arbitrary scaling variable (so m(i)=1 makes 10x10, m(i)=2 makes 9x9, etc.). Also, I replaced your function with the rand function because your function was making non-invertible matrices every time. Take a look at matrices A and Ai and see if it what you are looking for.