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/* cdf/cdf_gamma.c
*
* Copyright (C) 2003 Jason Stover.
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/
/*
* Author: J. Stover
*/
#include <config.h>
#include <math.h>
#include <gsl/gsl_cdf.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_sf_gamma.h>
double
gsl_cdf_gamma_P (const double x, const double a, const double b)
{
double P;
double y = x / b;
if (x <= 0.0)
{
return 0.0;
}
if (y > a)
{
P = 1 - gsl_sf_gamma_inc_Q (a, y);
}
else
{
P = gsl_sf_gamma_inc_P (a, y);
}
return P;
}
double
gsl_cdf_gamma_Q (const double x, const double a, const double b)
{
double Q;
double y = x / b;
if (x <= 0.0)
{
return 1.0;
}
if (y < a)
{
Q = 1 - gsl_sf_gamma_inc_P (a, y);
}
else
{
Q = gsl_sf_gamma_inc_Q (a, y);
}
return Q;
}
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