x = [0 1.25 1.85 2.4 3.05 3.64 4.25 4.85 5.45]
y = [0 4 6 8 10 12 14 16 18]
lp = lagrange(x, y)
polyval(lp, 2)
xplot = linspace(0,6,100); plot(xplot, polyval(lp, xplot));
hold on; plot(x, y, 'o'); hold off;