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/* gdtrl.c
*
* Gamma distribution function
*
*
*
* SYNOPSIS:
*
* long double a, b, x, y, gdtrl();
*
* y = gdtrl( a, b, x );
*
*
*
* DESCRIPTION:
*
* Returns the integral from zero to x of the gamma probability
* density function:
*
*
* x
* b -
* a | | b-1 -at
* y = ----- | t e dt
* - | |
* | (b) -
* 0
*
* The incomplete gamma integral is used, according to the
* relation
*
* y = igam( b, ax ).
*
*
* ACCURACY:
*
* See igam().
*
* ERROR MESSAGES:
*
* message condition value returned
* gdtrl domain x < 0 0.0
*
*/
/* gdtrcl.c
*
* Complemented gamma distribution function
*
*
*
* SYNOPSIS:
*
* long double a, b, x, y, gdtrcl();
*
* y = gdtrcl( a, b, x );
*
*
*
* DESCRIPTION:
*
* Returns the integral from x to infinity of the gamma
* probability density function:
*
*
* inf.
* b -
* a | | b-1 -at
* y = ----- | t e dt
* - | |
* | (b) -
* x
*
* The incomplete gamma integral is used, according to the
* relation
*
* y = igamc( b, ax ).
*
*
* ACCURACY:
*
* See igamc().
*
* ERROR MESSAGES:
*
* message condition value returned
* gdtrcl domain x < 0 0.0
*
*/
/* gdtrl() */
/*
Cephes Math Library Release 2.3: March, 1995
Copyright 1984, 1995 by Stephen L. Moshier
*/
#include <math.h>
#ifdef ANSIPROT
extern long double igaml ( long double, long double );
extern long double igamcl ( long double, long double );
#else
long double igaml(), igamcl();
#endif
long double gdtrl( a, b, x )
long double a, b, x;
{
if( x < 0.0L )
{
mtherr( "gdtrl", DOMAIN );
return( 0.0L );
}
return( igaml( b, a * x ) );
}
long double gdtrcl( a, b, x )
long double a, b, x;
{
if( x < 0.0L )
{
mtherr( "gdtrcl", DOMAIN );
return( 0.0L );
}
return( igamcl( b, a * x ) );
}
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