longge.m

牛顿迭代法

% 龙格现象
% r --- 常数
a=-5; b=5; h=(b-a)/10;
for r=1:3
x=[a:h:b]; y=1./(r.^2+x.^2);
xx=[a:0.01:b]; yy=1./(r.^2+xx.^2); 
m=length(xx); zz=zeros(1,m);
for j=1:m
    zz(j)=lagelangrichazhi(x, y, xx(j));
end
plot(xx,yy,xx,zz,'r:');hold on;grid on;xlabel('x');ylabel('y');
title('原函数与插值函数曲线比较图');
end
legend('r为1时原函数曲线','r为1时插值函数曲线','r为2时原函数曲线','r为2时插值函数曲线','r为3时原函数曲线','r为3时插值函数曲线');
text(-0.9,1.1,'常数r为1时');
text(-0.9,0.3,'常数r为2时');
text(-0.9,0.05,'常数r为3时');