nc=10; dc=[1,2,0]; ts=0.25; 
kp=1.0468; kd=0.2134; ki=1.2836; 
[nz1,dz1]=c2dm(nc,dc,ts); 
nz2=[kp*ts+kd+ki*ts*ts,-(kp*ts+2*kd),kd];dz2=[ts,-ts,0]; 
[nzk,dzk]=series(nz2,dz2,nz1,dz1); 
[nt,dt]=cloop(nzk,dzk,-1); 
dstep(nt,dt) 
figure;axis([-1.1 1.1 -1.1 1.1]); axis('square'); 
zgrid('new'); 
rlocus(nzk,dzk);grid