4.txt

包括牛顿法

>> x=[-5:0.5:5];
y=1./(1+x.^2);
i=[0:1:20];
xh=5*cos(i.*pi/20);
yh=langrange(x,y,xh);
x=xh;
y=1./(1+x.^2);
plot(xh,yh,'r--',x,y)
>> 


>> x=[-5:0.5:5];
y=1./(1+x.^2);
>> a=lagran(x,y)

a =

  Columns 1 through 11 

    0.0000   -0.0000   -0.0000   -0.0000    0.0000   -0.0000   -0.0002   -0.0000    0.0031   -0.0000   -0.0251

  Columns 12 through 21 

    0.0000    0.1263    0.0000   -0.3916   -0.0000    0.7534   -0.0000   -0.9657   -0.0000    1.0000

>> xh=5*cos(i.*pi/20);
yh=langrange(x,y,xh);
x=xh;
y=1./(1+x.^2);
plot(xh,yh,'r--',x,y)