hold off;

n=20;
h=10/n;



% Cubic spline with n  (equally spaced) nodes
x=-5:h:5;
y=1./(1+x.*x);
xi=-5:.01:5;
yi=spline(x,y,xi);
plot(xi,yi,'k')

hold on;

% Plot the original function
yi=1./(1+xi.*xi);
plot(xi,yi,'b');