% polynomial fit of Runge's function
x = (-1: 0.2: 1)';
y = 1./(1+25*x.^2); 
p = polyfit(x,y,10)
f = polyval(p,x); 
table = [x y f y-f]
xx=(-1:0.01:1)';
yy = 1./(1+25*xx.^2);
ff = polyval(p,xx);
plot(xx,yy,'o',xx,ff)