Why there is an error in my code after I type "[L,U] = eluinv(A);"? ( the error is that too many output arguments ) Thank you!

Here is the function:

function [] = eluinv(A)
[~,n]=size(A);
[L,U] = lu(A);
format compact
%have to round to supress extra zeroes
if (closetozeroroundoff(A) == closetozeroroundoff(round(L * U)))
 disp('Yes, I have got LU factorization')
end
%comparing the reduced row echelon forms of each
if closetozeroroundoff(rref(U)) == closetozeroroundoff(rref(A))
 disp('U is an echelon form of A')
else
 disp('Something is wrong')
end
%if is invertible, code will continue and inversion will occur
if rank(A) ~= min(size(A))
 sprintf('A is not invertible')
 invA=[];
 return
else
 eyeForL = [L eye(n)];
 eyeForU = [U eye(n)];
 aux = rref(eyeForL);
 aux2 = rref(eyeForU);
 invL = aux(:,(n+1):size(aux,2));
 invU = aux2(:,(n+1):size(aux2,2));
 invA = invU*invL;
 P = inv(A);
 if (closetozeroroundoff(invA - P) == zeros(size(A)))
 disp('Yes, LU factorization works for calculating the inverses')
 else
 disp('LU factorization does not work for me?')
 end
end

Answer 1

[Walter Roberson]

function [] = eluinv(A)

You declared that eluinv() does not return any values.

[L,U] = eluinv(A)

When you call a function and assign the output to variable names, MATLAB never looks inside the function to see if it can find variables with the same name to return the values of. Output in MATLAB is strictly positional. The first output location will be assigned the value of the first variable mentioned in the [] on the left side of the = in the function statement.

[Tianlan Yang]

Got it. Thank you!