Matlab实现——Lagrange approximation

 lagran.m

%Program 4.1  (Lagrange approximation)function [C,L]=lagran(X,Y)%Input  - X is a vector that contains a list of abscissas%       - Y is a vector that contains a list of ordinates%Output - C is a matrix that contains the coefficents of%         the Lagrange interpolatory polynomial%       - L is a matrix that contains the Lagrange%         coefficient polynomialsw=length(X); n=w-1; L=zeros(w,w);%Form the Lagrange coefficient polynomialsfor 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   end   L(k,:)=V;end%Determine the coefficients of the Lagrange interpolator polynomialC=Y*L;

untitled.m

X=[0,0.2,0.4,0.6,0.8,1];Y=[1,2.7183^0.2,2.7183^0.4,2.7183^0.6,2.7183^0.8,2.7183];[C,L]=lagran(X,Y)