x=[1 4 6];fx=log(x);
n=length(x);
xx=2;
f(xx)=0; %initialize summation
for ii=[1:n];
	Li=1; %initialize product calculation
	for j=[1:n];
		if(j~=ii);
			Li=Li*(xx-x(j))/(x(ii)-x(j));
		else
		end
	end
	f(xx)=f(xx)+Li*fx(ii);
end
f(xx)