Convert transfer function filter parameters to zero-pole-gain form

`[`

finds the matrix of zeros `z`

,`p`

,`k`

] = tf2zp(`b`

,`a`

)`z`

, the vector of poles
`p`

, and the associated vector of gains `k`

from the
transfer function parameters `b`

and `a`

. The function
converts a polynomial transfer-function representation

$$H(s)=\frac{B(s)}{A(s)}=\frac{{b}_{1}{s}^{n-1}+\cdots +{b}_{n-1}s+{b}_{n}}{{a}_{1}{s}^{m-1}+\cdots +{a}_{m-1}s+{a}_{m}}$$

of a single-input/multi-output (SIMO) continuous-time system to a factored transfer function form

$$H(s)=\frac{Z(s)}{P(s)}=k\frac{(s-{z}_{1})(s-{z}_{2})\cdots (s-{z}_{m})}{(s-{p}_{1})(s-{p}_{2})\cdots (s-{p}_{n})}.$$

Use `tf2zp`

when working with positive powers (*s*^{2} + *s* +
1), such as in continuous-time transfer functions. A similar function,
`tf2zpk`

, is more useful when working with
transfer functions expressed in inverse powers (1 + *z*^{–1} +
*z*^{–2}).