cofactors

This is a function that computes the cofactors of an n x n matrix

Description

When a user enters an n x n matrix eg. A=[1 1 1; 3 1 -1; 2 1 -1] the function computes the corresponding cofactors.

• MATLAB release: MATLAB 7.8 (R2009a)

[Sean de]

The output is not preallocated and grows inside the loop: M-LINT!!!

This will do the same thing faster (with preallocating output):
[r,c]=size(A);
[rr cc] = meshgrid(1:r,1:c);
D = zeros(r,c);
for ii = 1:numel(A)
    D(ii) = det(A(~(rr(ii)==1:r),~(cc(ii)==1:c)));
end
Ab = (-1).^(rr+cc).*D';

[Bruno Luong]

Cofactor_of_a = inv(a).'*det(a)

Simpler and faster.

Bruno

[Mark]

Bruno's suggestion only works for invertible matrices