拉格朗日插值matlab程序.docx

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1、拉格朗日插值的调用函数functiony=lagrange(x0,y0,x)n=length(x0);m=length(x);fori=1:mz=x(i);L=0.0;forj=1:nT=1.0;fork=1:nifk~=jT=T*(z-x0(k))/(x0(j)-x0(k));endendL=T*y0(j)+L;endy(i)=L;end四个图在一起：x=[-1:0.05:1];y=1./(1+25*x.^2);x0=[-1:0.4:1];y0=1./(1+25*x0.^2);y1=lagrange(x0,y0,x);x0=[-1:0.2

2、:1];y0=1./(1+25*x0.^2);y2=lagrange(x0,y0,x);x0=[-1:0.1:1];y0=1./(1+25*x0.^2);y3=lagrange(x0,y0,x);plot(x,y,'-r')holdonplot(x,y1,'-b',x,y2,'-r',x,y3,'-r')l5和fx在一起：x=[-1:0.05:1];y=1./(1+25*x.^2);x0=[-1:0.4:1];y0=1./(1+25*x0.^2);y1=lagrange(x0,y0,x);plot(x,y,'-r')holdonplot(x

3、,y1,'-b')l10和fx在一起：x=[-1:0.05:1];y=1./(1+25*x.^2);x0=[-1:0.2:1];y0=1./(1+25*x0.^2);y2=lagrange(x0,y0,x);plot(x,y,'-r')holdonplot(x,y2,'-b')l20和fx在一起：x=[-1:0.05:1];y=1./(1+25*x.^2);x0=[-1:0.1:1];y0=1./(1+25*x0.^2);y3=lagrange(x0,y0,x);plot(x,y,'-r')holdonplot(x,y3,'-b')