Description

These functions compute the Gauss error function and its complement. Both work with double precision floating point numbers and return a result of that type.

:  erf	error function: erf(x) = (2/sqrt(pi)) * integral from 0 to x of exp(-t^2) dt.
:  erfc	complementary error function: erfc(x) = 1 - erf(x), computed accurately for large x.
    

For large positive x, erfc avoids the loss of significance that would occur when computing 1 - erf (x) directly.