newtint.m

来自「这是用牛顿法做的」· M 代码 · 共 22 行

%使用均差进行多项式插值
function [yhat,dy,cout]=newtint(x,y,xhat)
n=length(y);if length(x)~=n,error('x and y are not compatible');end
c=y(:);
for j=2:n
    for i=n:-1:j
        c(i)=(c(i)-c(i-1))/(x(i)-x(i-j+1));
    end 
end
yhat=c(n);
for i=n-1:-1:1
    yhat=yhat.*(xhat-x(i))+c(i);
end
if nargout>1
    yn2=c(n-1);
    for i=n-2:-1;1
        yn2=yn2.*(xhat-x(i))+c(i);
    end
    dy=yhat-yn2;
    if nargout>2,cout=c;end
end