function [C,L] = lagran(X,Y)

w=length(X);

n=w-1;

L=zeros(w,w);



for k=1 : n+1

V=1;

for j=1 : n+1

if k~=j

V=conv(V,poly(X(j)))/(X(k)-X(j));

end %inner loop

end %outer loop

L(k,":")=V;

end



C=Y*L;