Finding the determinant without det(a)

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Ryan Driver on 27 Jan 2022
Edited: DGM on 27 Jan 2022
I need to physically computate the determinant of 3x3 matrices and lower without using the det(a) function, rather loops. What's causing this error?
DGM on 27 Jan 2022
Edited: DGM on 27 Jan 2022
Like Max, I'm guessing that matrix a1 isn't the expected size. In the future, it's best to post the code as formatted code instead of pictures so that people can troubleshoot it.
I'm just going to throw this out there. You can reuse the code for calculating the 2x2 case.
A = rand(3);
DA1 = det(A)
DA1 = 0.0476
DA2 = det33(A)
DA2 = 0.0476
function D = det22(A)
D = prod(A([1 4])) - prod(A([2 3]));
end
function D = det33(A)
D = A(1,1)*det22(A(2:3,2:3)) - A(1,2)*det22(A(2:3,[1 3])) + A(1,3)*det22(A(2:3,1:2));
end

Max Heimann on 27 Jan 2022
Edited: Max Heimann on 27 Jan 2022
According to the error you are trying to access an index which is not part of the variable.
Are you sure a1 is a 3x3 matrix?
It looks like you are calling the function with a 2x3 matrix [1 2 3; 4 5 6]
Ryan Driver on 27 Jan 2022
Stupid mistake. Thank you.