How can I factorise 4th order Transfer functions?

I am currently working on investigating time responses for Transfer functions which I have entered into Matlab.

The current Transfer function I have produced is shown below; sys =

           -0.64 s^2 - 0.4104 s + 0.00783
  -------------------------------------------------
  s^4 + 1.489 s^3 + 0.7681 s^2 + 0.09455 s + 0.0424

I now need to analyse the natural frequency and damping ratio's in the system's response. To do this, I need to display the 4th-order denominator as two 2nd-order responses. To do this, I know the denominator needs to be factorised.

Using Matlab, is it possible to factorise a 4th-order response using a command or sequence of commands? If so, could anyone please provide me with a script example of how to do this?

I apologise if I am being unclear in my question. I can elaborate if need be.

Answer 1

[Azzi Abdelmalek]

Look at this example

sys=tf([-0.64 -0.4101 0.00783],[1 1.489 0.7681 0.09455 0.0424])

You can find the poles and zeros transfer function

poles=roots(cell2mat(sys.Den))
zeros=roots(cell2mat(sys.Num))