herm.m

已知两个点要求用插值的方法绘制拟和的曲线 此文件是拟和飞机下降曲线

function yi= herm(x,y,ydot,xi)
n1 = length(x);n2 = length(y);n3 = length(ydot);
%输入的x,y,ydot的个数必须相同
if n1 ~=n2 | n1~=n3 | n2~=n3
    error('The length of X,Y and Ydot must equal!');
    return;
end
for k=1:n1-1
    if abs(x(k)-x(k+1)) < eps  
        %插值节点必须互异
        error('the Data is wrong!');
        return;
    end
    if x(k) <= xi & xi <= x(k+1)
        yi=y(k)*(1+2*(xi-x(k))/(x(k+1)-x(k)))*(x(k+1)-xi)^2/(x(k+1)-x(k))^2 ...
            + y(k+1)*(1+2*(x(k+1)-xi)/(x(k+1)-x(k)))*(x(k)-xi)^2/(x(k+1)-x(k))^2 ...
            +ydot(k)*(xi-x(k))*(x(k+1)-xi)^2/(x(k+1)-x(k))^2 ...
            +ydot(k+1)*(xi-x(k+1))*(x(k)-xi)^2/(x(k+1)-x(k))^2 ;
        return;
    end
end