vzoreček pro výpočet kv. rovnice poskytl 
Tomáš Studený xstude02@stud.fit.vutbr.cz

% aux pro diskretni systemy 

%%%%%%%%%%%%%%%%%%%%%%%% H pro filtr 3 2 1
n = 0:2; Fs = 8000; gj0 = find(n==0); T = 1/Fs; 
x = [3 2 1]; 
subplot(311); stem(n,x); grid; title('h')
f = -2*Fs:100:2*Fs; 
fn = f / Fs; 
Om = 2*pi*f;
om = Om / Fs; 
% dtft
X = zeros(size(om)); 
for ii=1:length(om)
  ejon = exp(j*om(ii).*n); 
  X(ii) = sum(x .* ejon); 
end
subplot(312); plot (om,abs(X)); grid; axis tight; title('module');
subplot(313); plot (om,angle(X)); grid; axis tight; title('phase');
print -depsc FIG/h.eps

subplot(221); plot (om,abs(X)); grid; axis tight; title('normalized omega');
subplot(222); plot (Om,abs(X)); grid; axis tight; title('omega');
subplot(223); plot (fn,abs(X)); grid; axis tight; title('normalized f');
subplot(224); plot (f,abs(X)); grid; axis tight;  title('f'); 
print -depsc FIG/hfs.eps

%%%%%%%%%%%%%%%%% priklady filtry %%%%%%%%%%%%%%%%%%%%%
H=freqz([1 0.5],[1],256); om=(0:255)/256 * pi;
subplot(211); plot(om,abs(H)); grid
subplot(212); plot(om,angle(H)); grid
print -depsc FIG/h_1+0.5.eps

zplane([1 0.5],[1]); 
print -depsc FIG/np_1+0.5.eps
%%% iir
n = 0:30;
y= filter([1],[1 0.5],[1 zeros(1,30)]); stem(n,y); 
print -depsc FIG/imp_rek_1+0.5.eps
H=freqz([1],[1 0.5],256); om=(0:255)/256 * pi;
subplot(211); plot(om,abs(H)); grid
subplot(212); plot(om,angle(H)); grid
print -depsc FIG/h_rek_1+0.5.eps

zplane([1],[1 0.5]); 
print -depsc FIG/np_rek_1+0.5.eps