# There are two errors in my code. Can someone know how to edit it to maker it run? Thank you!

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Tianlan Yang on 18 Mar 2021
Commented: Tianlan Yang 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(size(L,1))];
ueye = [U eye(size(U,1))];
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)),zeros(size(A)))
disp('Yes, LU factorization works for calculating the inverses')
else
disp('LU factorization does not work for me?!')
end
end

Cris LaPierre on 18 Mar 2021
The error message appears to show the reason for the error. Your matrix A must be square (3x3 or 4x4) in order to use inv.
if isequal(closetozeroroundoff(invA-inv(A)),zeros(size(A)))
^^^^^^ % Error is here
Tianlan Yang on 18 Mar 2021
That works. Thanks