function srt03Nyquist0

% SRT Rechnerdemo 3
% WS 2000-2001
% Klaus Schmid, 23.10.2000 / Eberhard Münz 28.11.2001

n=[-5];
p=[-2 -3 -1+j -1-j];

% k=evalin('base','k');
k_all={10; 5; 15};

% Übertragungsfunktion berechnen
for r=1:size(k_all,1)
    k=k_all{r,1}
    
System = zpk(n,p,k)

re=[];
im=[];

for w=0:0.03:20
   nenner=1;
   zaehler=k;
   for m=1: length(p)
      nenner=(i*w-p(m))*nenner;
   end
   for m=1:length(n)
      zaehler=(i*w-n(m))*zaehler;
   end
   
   re=[re;real(zaehler/nenner)];
   im=[im;imag(zaehler/nenner)];
   
end

re_all{r,1}=re;
im_all{r,1}=im;
end;

if isempty(findobj('tag','srt03nyquist01'))
    fig=figure;
    set (fig,'tag','srt03nyquist01','Name','Nyquist-Ortskurve für verschiedene k');
else
    figure(findobj('tag','srt03nyquist01'));
end

%plot([-2;2],[0; 0],'gr');
%hold on;
%plot([0; 0],[-2; 2],'gr');
%hold on;
plot(-1,0,'+r','Linewidth',2);
hold on;
plot(-1.5,0,'w');
hold all;
for r=1:size(k_all,1)
h(r)=plot(re_all{r,1},im_all{r,1});
end;
%axes;
grid on;
hold off;
legend([h(1),h(2),h(3)],'k=10','k=5','k=15','Location','SE');