How to display column vector x in Cramer's rule in MATLAB? - matlab

Question

I am trying to code the Cramer's Rule on MATLAB for a square matrix. I understand the Rule perfectly and also believe the logic behind my code is alright. However, could you please check where I might be going wrong that my result is not being displayed correctly? Any help would be appreciated! Thanks :)
function x = cramer(A, b)
r = size(A, 1);
c = size(A, 2);
n = size(b, 1);
if r ~= c
disp('Oops! Please enter a square matrix');
end
if r == c == n
D = det(A);
if D == 0
disp('Oops! Either, there are a family of soultions or no unique solution')
end
if D ~= 0
result = zeros(n, 1);
for (i = 1:n)
A_x = A;
A_x(:, i) = b;
Dx = det(A_x);
result(i,1) = Dx/D;
end
x = result;
end
end
end

Answer 1

You have an error in your if r == c == n check.
The expression r == c == n can be expanded as (r == c) == n
So it compares the value of logical(r == c) with n.
As an example:
>> 2 == 2 == 1
ans =
logical
1
Rewrite your check as r == c && c == n or isequal(r,c,n) and you should be good.
EDIT: You can simplify your logic quite some, say for example by:
function x = cramers(A, b)
if diff(size(A)) && size(A,1) == n
D = det(A);
if D == 0
disp('Oops! Either, there are a family of solutions or no unique solution')
return
else
result = zeros(n, 1);
for i = 1:n
A_x = A;
A_x(:, i) = b;
Dx = det(A_x);
result(i,1) = Dx/D;
end
x = result;
end
else
disp('Dimension error')
return
end
end