erf(3F)                                                   erf(3F)



NAME
     erf, erfc - error function and complementary error function

SYNOPSIS
     double precision function erf (x)
     double precision x;

     double precision function erfc (x)
     double precision x;

DESCRIPTION
     erf returns the error function of x, defined as

     2 / sqrt(Pi) * integral[0, x] exp(-(t**2)) dt

     erfc, which returns 1.0 - erf(x), is provided because of the
     extreme loss of relative accuracy if erf(x) is called for
     large x and the result subtracted from 1.0 (e.g., for x = 5,
     12 places are lost).

SEE ALSO
     exp(3F).

NOTES
     When compiling source with the -Qocs option, an explicit
     underscore needs to be added to the end of the routine
     names.




























Page 1                        CX/UX Hf77 Fortran Reference Manual