function f = Atken(x,y,x0)
syms t;
if(length(x) == length(y))
    n = length(x);    
else
    disp('x和y的維數不相等！');
    return;
end                                      %檢錯

y1(1:n) = t;                             %符號函數數組要賦初值
for(i=1:n-1)   
    for(j=i+1:n)
        y1(j) = y(j)*(t-x(i))/(x(j)-x(i))+y(i)*(t-x(j))/(x(i)-x(j));    
    end
    y = y1;
    simplify(y1);
end

if(nargin == 3)
    f = subs(y1(n),'t',x0);            %計算插值點的函數值
else
    simplify(y1(n));                   %化簡
    f = collect(y1(n));                %將插值多項式展開
    f = vpa(f,6);                      %將插值多項式的系數化成6位精度的小數
end