% Lagrange polinom
x = [2 2.25 2.5 2.75]
y = [3 55/16 5/2 -3/16]
% gyoktenyezok
p1 = [1 -2]
p2 = [1 -2.25]
p3 = [1 -2.5]
p4 = [1 -2.75]
% Lagrange segedpolinomok
l1 = conv(conv(p2,p3), p4);
l1 = l1/polyval(l1,2)
l2 = conv(conv(p1,p3), p4);
l2 = l2/polyval(l2,2.25)
l3 = conv(conv(p1,p2), p4);
l3 = l3/polyval(l3,2.5)
l4 = conv(conv(p1,p2), p3);
l4 = l4/polyval(l4,2.75)
% Lagrange poli
L = y(1) * l1 + y(2) * l2 + y(3)*l3 + y(4)*l4
% abra
t = 1:0.1:4;
plot(t,polyval(L,t),x,y,'*')