# create a plot of effective index vs fraction

npts=10;
fraction=linspace(0,1,npts);
lambda=1e-6;

n_mode=matrix(npts);
n_material=matrix(npts);

for (i=1:npts) {
  switchtolayout;
  name="fractional material";
  setmaterial(name,"x3",fraction(i));
  
  setanalysis("wavelength",lambda);
  findmodes;
  n_mode(i)=getdata("mode1","neff");
  n_material(i)=getindex("fractional material",lambda);
}
plot(fraction,n_mode,n_material,"fraction of material A","index");
legend("mode effective index","material index");