% 龍格現象
% r --- 常數
a=-5; b=5; h=(b-a)/10;
for r=1:0.5:2
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('原函數與插值函數曲線比較圖');
end
legend('r為1時原函數曲線','r為1時插值函數曲線','r為1.5時原函數曲線','r為1.5時插值函數曲線','r為2時原函數曲線','r為2時插值函數曲線');
text(-1.1,1.1,'常數r為1時');
text(-0.9,0.5,'常數r為1.5時');
text(-0.9,0.2,'常數r為2時');