Hello,
Looking at the function ss2tf - which converts state space to transfer
function I am trying to understand how the numerator polynomial is
calculated. I understand how the denominator polynomial is calculated,
but can't figure out how the numerator works out.

The numerator is calculated by: num = det(sI- A +BC) -det(sI-A)

note: A, B, C, D are the regular state space matrices (in this case D=0). So the numerator comes from the eigenvalues of the matrix A-BC and the matrix A

I would be grateful for hints in the derivation or a pointer to a paper.

Thanks. David

The numerator is calculated by: num = det(sI- A +BC) -det(sI-A)

note: A, B, C, D are the regular state space matrices (in this case D=0). So the numerator comes from the eigenvalues of the matrix A-BC and the matrix A

I would be grateful for hints in the derivation or a pointer to a paper.

Thanks. David