The x = erfinv(y) function is the inverse error function. The value of y must be in the interval [-1, 1]. It satisfies the error function y = erf(x) for -1 ≤ y ≤ 1 and -∞ ≤ x ≤ +∞.


y (input, double) 
The argument y of the function, must be within the range [-1, 1]
x (output, double)
The return value of the inverse error function for specified y.