function yy=lagrange(x,y,xx)
m=length(x);
n=length(xx);
for k=1:n;
    s=0.0;
    for i=1:m;
        q=1.0;
        for j=1:m;
            if i~=j;
               q=q*(xx(k)-x(j))/(x(i)-x(j));
           end
       end
       s=s+q*y(i);
   end
   yy(k)=s;
end