newton.m

在Matlab中

function s=Newton(x,y,x0,nn)
nx=length(x);
ny=length(y);
if nx~=ny
    warning('向量x与y的长度应该相同');
    return;
end
m=length(x0);
%according to formula,calculate x0 that will get
for i=1:m
    t=0.0;
    j=1;
    yy=y;
    kk=j;
    %find  averge diff of every grade
    while(kk<=nn)
        kk=kk+1;
        for k=kk:nx
            yy(k)=(yy(k)-yy(kk-1))/(x(k)-x(kk-1));
        end
    end
    %get result of diff
    t=yy(1);
    for k=2:nn
        u=1.0;
        jj=1;
        while(jj<k)
            u=u*(x0(i)-x(jj));
            jj=jj+1;
        end
        t=t+yy(k)*u;
    end
    s(i)=t;
end
return