runge.m

MATLAB实现拉格朗日、分段线性、三次样条三种插值的方法

m=101;
x=-5:10/(m-1):5;
t=zeros(1,36);l=-1.5:0.1:2;
y=1./(1+x.^2);z=0*x;plot(x,z,'r',x,y,'k:',t,l),gtext('y=1/(1+x^2)'),pause
n=3;
x0=-5:10/(n-1):5;
y0=1./(1+x0.^2);
y1=lagr1(x0,y0,x);hold on,plot(x,y1,'b'),gtext('n=2'),pause,hold off
n=5;
x0=-5:10/(n-1):5;
y0=1./(1+x0.^2);
y2=lagr1(x0,y0,x);hold on,plot(x,y2,'b:'),gtext('n=4'),pause,hold off

n=7;
x0=-5:10/(n-1):5;
y0=1./(1+x0.^2);
y3=lagr1(x0,y0,x);hold on,plot(x,y3,'r'),gtext('n=6'),pause,hold off
n=9;
x0=-5:10/(n-1):5;
y0=1./(1+x0.^2);
y4=lagr1(x0,y0,x);hold on,plot(x,y4,'r:'),gtext('n=8'),pause,hold off
n=11;
x0=-5:10/(n-1):5;
y0=1./(1+x0.^2);
y5=lagr1(x0,y0,x);hold on,plot(x,y5,'m'),gtext('n=10')