nag_erfc (s15adc) returns the value of the complementary error function, .

nag_erfc (s15adc) calculates an approximate value for the complement of the error function

The approximation is based on a Chebyshev expansion.

If  and  are relative errors in the argument and result, respectively, then in principle , so that the relative error in the argument, , is amplified by a factor  in the result.

Near  this factor behaves as  and hence the accuracy is largely determined by the machine precision. Also for large negative , where the factor is , accuracy is mainly limited by machine precision. However, for large positive , the factor becomes  and to an extent relative accuracy is necessarily lost. The absolute accuracy  is given by  so absolute accuracy is guaranteed for all .

None.