拉格朗日 优美典范

Posted 2022-02-09 飞凡可期

%syms： good lagrange 朗格朗日好样的； %两种方式1：x=x0, eval(f1); 2:使用x,y,x,y subs替换函数，属性-值的花括号（元组对）即可；
syms x1 x2 x3 x4 x x5 x6
exp = (x-x2)*(x-x3)*(x-x4)/((x1-x2)*(x1-x3)*(x1-x4))
f1 = subs(exp, x,x1,x2,x3,x4,0,-2,-1,1,2)
f2 = subs(exp, x,x1,x2,x3,x4,0,-1,-2,1,2)
f3 = subs(exp, x,x1,x2,x3,x4,0,1,-2,-1,2)
f4 = subs(exp, x,x1,x2,x3,x4,0,2,-2,-1,1)
% changed to 1~4
f1 = subs(exp, x,x1,x2,x3,x4,3,1,2,4,5)
f2 = subs(exp, x,x1,x2,x3,x4,3,2,1,4,5)
f3 = subs(exp, x,x1,x2,x3,x4,3,4,1,2,5)
f4 = subs(exp, x,x1,x2,x3,x4,3,5,1,2,4)
% gap2
f1 = subs(exp, x,x1,x2,x3,x4,0,-4,-2,2,4)
f2 = subs(exp, x,x1,x2,x3,x4,0,-2,-4,2,4)
f3 = subs(exp, x,x1,x2,x3,x4,0,2,-4,-2,4)
f4 = subs(exp, x,x1,x2,x3,x4,0,4,-4,-2,2)

%middle gap 2 - 0;
f1 = subs(exp, x,x1,x2,x3,x4,0,-3,-2,2,3)
f2 = subs(exp, x,x1,x2,x3,x4,0,-2,-3,2,3)
f3 = subs(exp, x,x1,x2,x3,x4,0,2,-3,-2,3)
f4 = subs(exp, x,x1,x2,x3,x4,0,3,-3,-2,2)
%middle gap 2 -  -1;
f1 = subs(exp, x,x1,x2,x3,x4,-1,-3,-2,2,3)
f2 = subs(exp, x,x1,x2,x3,x4,-1,-2,-3,2,3)
f3 = subs(exp, x,x1,x2,x3,x4,-1,2,-3,-2,3)
f4 = subs(exp, x,x1,x2,x3,x4,-1,3,-3,-2,2)

%middle gap 3 - 0;
f1 = subs(exp, x,x1,x2,x3,x4,0,-4,-3,3,4)
f2 = subs(exp, x,x1,x2,x3,x4,0,-3,-4,3,4)
f3 = subs(exp, x,x1,x2,x3,x4,0,3,-4,-3,4)
f4 = subs(exp, x,x1,x2,x3,x4,0,4,-4,-3,3)

!](https://img-blog.csdnimg.cn/7ef9263085a9445b8a09c0ce87db642f.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA6aOe5Yeh5Y-v5pyf,size_20,color_FFFFFF,t_70,g_se,x_16)