Here are three ways to define a transfer function model. From the documentation, it seems to me that all three should produce the same thing. But the third case, which specifies {nunerator, denominator} = {a, b s} seems to result in something different. What is it I am misunderstanding?
If you look at the notes under the section, Details and Options, it says you have to specify num as a matrix… den can be specified as a matrix or just a denominator.