Can someone solve this Error for me? Thank you

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Tianlan Yang
Tianlan Yang on 18 Mar 2021
Commented: KSSV on 18 Mar 2021
Here is the function:
function [L,U] = eluinv(A)
[~,n]=size(A);
[L,U] = lu(A);
format compact
if closetozeroroundoff(A,7) == closetozeroroundoff(L*U,7)
disp('Yes, I have got LU factorization')
end
if closetozeroroundoff(rref(U),7) == closetozeroroundoff(rref(A),7)
disp('U is an echelon form of A')
else
disp('Something is wrong')
end
if rank(A) ~= min(size(A))
sprintf('A is not invertible')
invA=[];
return
else
leye = [L eye(n)];
ueye = [U eye(n)];
invLech = rref(leye);
invUech = rref(ueye);
invL = invLech(:,(n+1):size(invLech,2));
invU = invUech(:,(n+1):size(invUech,2));
invA = invU*invL;
if isequal(closetozeroroundoff(invA-inv(A),7),zeros(size(A)))
disp('Yes, LU factorization works for calculating the inverses')
else
disp('LU factorization does not work for me?!')
end
end

Answers (1)

KSSV
KSSV on 18 Mar 2021
Replace lines:
leye = [L eye(n)];
ueye = [U eye(n)];
with:
leye = [L eye(size(L,1))];
ueye = [U eye(size(U,1))];
  2 Comments
Tianlan Yang
Tianlan Yang on 18 Mar 2021
That works. However, there exist another mistake. Can you help solve this as well?
KSSV
KSSV on 18 Mar 2021
This error is clear, if you want to find the inverse of a matrix, the matrix should be a square matrix.

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