function lagrange(x,y,xx)
n=length(x);m=length(y);
if m~=n
    error('輸入x和y的個(gè)數(shù)不相等!\n');
    return;
end
a=1;b=0;
for i=1:n
    a=a*(xx-x(i));
end
for j=1:n
    c=1;
    for i=1:n   
        if i~=j
            c=c*(x(j)-x(i));
        end
    end                               
    b=b+(y(j)*a)/((xx-x(j))*c); 
end
fprintf('\nthe result is :f(x)=%f',b);