lagrange.m

数值分析方法,主要里面涵盖了计算方法方面matlab程序！

clear
clc
%function lagrint(x,y,xi)
x=[0.56160 0.56280 0.56401 0.56521]';
y=[0.82741 0.82659 0.82577 0.82495]';
xi=0.5635;
dxi=xi-x;
n=length(x);
L=zeros(size(y));
L(1)=prod(dxi(2:n))/prod(x(1)-x(2));
L(n)=prod(dxi(1:n-1))/prod(x(n)-x(1:n-1));
for j=2:n-1
    num=prod(dxi(1:j-1))*prod(dxi(j+1:n));
    den=prod(x(j)-x(1:j-1))*prod(x(j)-x(j+1:n));
    L(j)=num/den;
end
yi=sum(y.*L);
fprintf('x=%f,y=%f\n',xi,yi);