blob: 04bd2747843e668dc2a474ece9f93134be1f0e9e [file] [log] [blame]
/*
* Mathlib : A C Library of Special Functions
* Copyright (C) 1998 Ross Ihaka
* Copyright (C) 2000-2015 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
* https://www.R-project.org/Licenses/
*
* DESCRIPTION
*
* The distribution function of the Weibull distribution.
*/
#include "nmath.h"
#include "dpq.h"
double pweibull(double x, double shape, double scale, int lower_tail, int log_p)
{
#ifdef IEEE_754
if (ISNAN(x) || ISNAN(shape) || ISNAN(scale))
return x + shape + scale;
#endif
if(shape <= 0 || scale <= 0) ML_ERR_return_NAN;
if (x <= 0)
return R_DT_0;
x = -pow(x / scale, shape);
return lower_tail
? (log_p ? R_Log1_Exp(x) : -expm1(x))
: R_D_exp(x);
}