l.m

利用牛顿、拉格朗日、三次样条及线性插值方法拟合数据

function L =L(x) %Lagrange
syms m
L=0;
r=1/(1+m^2);
X=0:20;f=1;
F=0:20;
l=0:20;
for i=1:21
    X(i)=5*cos((2*i-1)*pi/42);
    f=f*(x-X(i));
end

for i=1:21
    F(i)=1;
    for j=1:21
        if i~=j
            F(i)=F(i)*(X(i)-X(j));
        end
    end
    l(i)=subs(r,'m',X(i));
    L=L+(l(i)*f)/((x-X(i))*F(i));
end