%
%  m-file for Example 8B.2 (Program 8B.2, p566).
%	Program name: prog8b2.m
%
N=2;											%	Filter order
Fs=1280;										%	Sampling frequency
FN=Fs/2;
fc=150;										%	Cutoff frequency
Fc=fc/FN;									%	Normalized Cutoff frequency
[b,a]=butter(N,Fc);						%	Create and digitize analogue filter.
[z,p,k]=butter(N, Fc);
subplot(2,1,1)								%	Plot magnitude freq. response
[H, f]=freqz(b, a, 512, Fs);			
plot(f, abs(H))
xlabel('Frequency (Hz)')
ylabel('Magnitude Response ')
subplot(2,1,2)								%	Plot pole-zero diagram
zplane(b, a)
b
a