Question on Filter implementation #717

I am interested in using the discrete transfer functions from the control library to filter signals and compute Fourier transforms.

For instance, given a discrete first order butterworth filter

from control import *

z = TransferFunction.z

c1 = 0.0196078431372549
c2 = -0.9607843137254902

Htest = c1*(1+z**(-1))/(1+c2*z**(-1))

How do I apply "Htest" on a signal "x" in order to obtain the filtered signal? Is there already a feature for that?

Likewise it would be very practical to use the transfer function of the Goertzel alg. to compute a fourier transform of a signal.

Thank you!

Hadamard-Zweistein