How to convert a transfer function model to a zero-pole-gain model?

Question

Mathematica has a function to convert TransferFunctionModels to StateSpaceModels:

mytf=TransferFunctionModel[(2 s + 3)/(s^3 + 4 s^2 + 5), s]
StateSpaceModel[mytf]

Is there a corresponding function that will convert to a zero-pole-gain model?

Answer 1

It turns out that there is a function that will do this but it is hidden from the user a little in an internal function

In[]:= Control`ZeroPoleGainModel[mytf]

Out[]=
Control`ZeroPoleGainModel[{{{{-(3/2)}}}, 
    {1/3 (-4 - 16 (2/(263 - 3 Sqrt[5865]))^(1/3) - 
     (1/2 (263 - 3 Sqrt[5865]))^(1/3)), 
     -(4/3) + 8/3 (1 + I Sqrt[3]) (2/(263 - 3 Sqrt[5865]))^(1/3) +
         1/6 (1 - I Sqrt[3]) (1/2 (263 - 3 Sqrt[5865]))^(1/3), 
     -(4/3) + 8/3 (1 - I Sqrt[3]) (2/(263 - 3 Sqrt[5865]))^(1/3) +
         1/6 (1 + I Sqrt[3]) (1/2 (263 - 3 Sqrt[5865]))^(1/3)}, 
    {{2}}}, s]

original source: http://www.walkingrandomly.com/?p=2799