core/vnl/vnl_erf.cxx File Reference

Complete and incomplete gamma function approximations. More...

#include "vnl_erf.h"

Go to the source code of this file.

Functions
double	vnl_erfc (double x)
	The Complementary Error function.

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Detailed Description

Complete and incomplete gamma function approximations.

Author:

Tim Cootes Translated from NETLIB/SPECFUN/erf by Ian Scott Original SPECFUN fortran based on the main computation evaluates near-minimax approximations from "Rational Chebyshev approximations for the error function" by W. J. Cody, Math. Comp., 1969, PP. 631-638.

Definition in file vnl_erf.cxx.

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Function Documentation

double vnl_erfc

(

double

x

)

The Complementary Error function.

erfc(x) = 1 - erf(x) = 1 - (2/sqrt(pi)) Integral from 0 to x (exp(-t^2) dt) This value is useful for large x, when erf(x) ~= 1 and erfc(x) < eps.

Note:

the output ranges from 0 to 2, and vnl_erfc(0) = 1.

Definition at line 13 of file vnl_erf.cxx.