matlab实现newton插值

男娘i 2022-01-28 15:01 361阅读 0赞

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newton.m

function s=newton(x,y,t)
    %计算输入的x y是否长度相等
    if(length(x)==length(y))
        n=length(x);
    else
        disp('x和y的维数不相等！');
        return;  
    end
     
    syms p;
    s=y(1);
    dd=zeros(1,100);
    dxs=1;
     
     
    for i=1:n-1
        for j=i+1:n
            dd(j)=(y(j)-y(i))/(x(j)-x(i));  %用来构造均差
        end
        temp(i)=dd(i+1);
        dxs=dxs*(p-x(i));
        s=s+temp(i)*dxs;
        y=dd;     %第一次将一阶均差赋给y，然后通过上面的dd(j)来构造二阶均差
        s=simplify(s);
        s=subs(s,'p',t);
        s=vpa(s,6);
    end

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