flagrange3.m

来自「自己编写的matlab程序 数值分析里的程序」· M 代码 · 共 13 行

%  flagrange3([2 3 4],[1 10 5],[2.5 3.5 4.5 5])
function y=flagrange3(x0,y0,z);
syms x
if length(x0)==3
   l1=(x-x0(2))*(x-x0(3))/((x0(1)-x0(2))*(x0(1)-x0(3)));
   l2=(x-x0(1))*(x-x0(3))/((x0(2)-x0(1))*(x0(2)-x0(3)));
   l3=(x-x0(1))*(x-x0(2))/((x0(3)-x0(1))*(x0(3)-x0(2)));
   y=simplify(y0(1)*l1+y0(2)*l2+y0(3)*l3);
   ezplot(y);
   subs(y,x,z)
else
   disp('input error')
end