/*
* Mathlib : A C Library of Special Functions
* Copyright (C) 2006 The R Core Team
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, a copy is available at
* http://www.r-project.org/Licenses/
*
* SYNOPSIS
*
* #include
*
* double pbeta_raw(double x, double pin, double qin, int lower_tail, int log_p)
* double pbeta (double x, double pin, double qin, int lower_tail, int log_p)
*
* DESCRIPTION
*
* Returns distribution function of the beta distribution.
* ( = The incomplete beta ratio I_x(p,q) ).
*
* NOTES
*
* As from R 2.3.0, a wrapper for TOMS708
* as from R 2.6.0, 'log_p' partially improved over log(p..)
*/
#include "nmath.h"
#include "dpq.h"
attribute_hidden
double pbeta_raw(double x, double pin, double qin, int lower_tail, int log_p)
{
double x1 = 0.5 - x + 0.5, w, wc;
int ierr;
bratio(pin, qin, x, x1, &w, &wc, &ierr, log_p); /* -> ./toms708.c */
/* ierr = 8 is about inaccuracy in extreme cases */
if(ierr && (ierr != 8 || log_p) )
MATHLIB_WARNING(_("pbeta_raw() -> bratio() gave error code %d"), ierr);
return lower_tail ? w : wc;
} /* pbeta_raw() */
double pbeta(double x, double pin, double qin, int lower_tail, int log_p)
{
#ifdef IEEE_754
if (ISNAN(x) || ISNAN(pin) || ISNAN(qin)) return x + pin + qin;
#endif
if (pin <= 0 || qin <= 0) ML_ERR_return_NAN;
if (x <= 0)
return R_DT_0;
if (x >= 1)
return R_DT_1;
return pbeta_raw(x, pin, qin, lower_tail, log_p);
}