//Zero interpolation and spectrum replication
XF=[0 1 2 1];
X1F=[XF XF XF 0];
YF=[X1F X1F];
DF=0.5*[XF XF 0];
GF=0.5*[XF 0 XF 0 XF 0];
f=-0.2:0.1:1;
f1=-0.1:0.05:1.15;
f2=-0.4:0.2:1.2;
f3=-0.2:0.1:1.2;
length(f3),length(GF)
a=gca();
a.y_location="origin";
subplot(211);
plot2d(f,X1F);
ylabel('X1F');
subplot(212);
a.y_location="origin";
plot2d(f1,YF);
ylabel('YF');
xset('window',1);
b=gca();
b.y_location="origin";
subplot(211);
plot2d(f2,DF);
ylabel('DF');
subplot(212);
b.y_location="origin";
plot2d(f3,GF);
ylabel('GF');