说明：  ERF函数的原代码,erf(x)=(2/根号下派)*(exp(-z方)对z积分，积分下限是0，上限是x)，误差函数从形式上很像正态分布的分布函数Φ(x)，是对一个形如正态分布的概率密度函数做变上限积分的结果；
(ERF function of the original code, erf (x) = (2/root allocation under No.)* (exp (-z side) of the z integral, integral lower limit is 0, the upper limit is x), error function from the form like normal distribution distribution function Φ (x), is a shape such as the normal distribution probability density function do change the results limit points )