用matlab如何编写牛顿迭代法问题,

function [ A ] = cal( a,b,v )%a,b表示区间,v是精度
i=1;
x = (a+b)/2;
A=[i x];
t = x-(x^3-x-1)/(3*x^2-1);%迭代函数
while(abs(t-x)>v)
i=i+1;
x = t;
A = [A;i x];
t = x-(x^3-x-1)/(3*x^2-1);%迭代函数
end
A = [A;i+1 t];
end
运行结果：
>> format long;
>> cal(1,2,0.00001)
ans =
1.000000000000000 1.500000000000000
2.000000000000000 1.347826086956522
3.000000000000000 1.325200398950907
4.000000000000000 1.324718173999054
5.000000000000000 1.324717957244790