xinit('analog.2.ps')
//         File polesp.ps
//square();          //Normalisation to get a square Basile window...
n=13;                 //Number of poles
angles=ones(1,n)*(%pi/2+%pi/(2*n))+(0:n-1)*%pi/n;
s=exp(%i*angles);     //Location of the poles
xset("mark",0,1)
plot2d(real(s)',imag(s)',[2],"012"," ",[-1.2,-1.2,1.2,1.2]);
xarc(-1,1,2,2,0,360*64);
xsegs([-1.2,0;1.2,0],[0,-1.2;0,1.2])
xtitle('Pole positions of Butterworth filter');
xend()
