Documentation

Make a filter from a rational polynomial in s. A rational polynomial in s is specified by the polynomial coefficients in the numerator and the denominator in descending order of s. Fails if for some reasons the roots can not be determined.

The formula is

zpk(s) = k \frac{a_n s^{n_z} + a_{n-1} s^{n_z - 1} \cdots}
{b_n s^{n_p} + b_{n-1} s^{n_p - 1} \cdots}$$
where $a_n$, $a_{n-1}$,..., $a_0$ are the coeffciients of the 
polynomial in the numerator and $b_n$, $b_{n-1}$,..., $b_0$ are
the coefficients of the polynomial in the denominator.
The polynomial coefficients have to be real.

Returns:

IIRFilter

Parameters:

fs - Sampling frequency
nnumer - Number of coefficients in numerator
numer - Array of numerator coefficents
ndenom - Number of coeffcients in denominator
denom - Array of denominator coeffcients
gain - Gain
prewarp - True for prewarping freqencies.