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- /* gdtr.c
- *
- * Gamma distribution function
- *
- *
- *
- * SYNOPSIS:
- *
- * double a, b, x, y, gdtr();
- *
- * y = gdtr( 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
- * gdtr domain x < 0 0.0
- *
- */
- /* gdtrc.c
- *
- * Complemented gamma distribution function
- *
- *
- *
- * SYNOPSIS:
- *
- * double a, b, x, y, gdtrc();
- *
- * y = gdtrc( 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
- * gdtrc domain x < 0 0.0
- *
- */
- /* gdtr() */
- /*
- Cephes Math Library Release 2.8: June, 2000
- Copyright 1984, 1987, 1995, 2000 by Stephen L. Moshier
- */
- #include <math.h>
- #ifdef ANSIPROT
- extern double igam ( double, double );
- extern double igamc ( double, double );
- #else
- double igam(), igamc();
- #endif
- double gdtr( a, b, x )
- double a, b, x;
- {
- if( x < 0.0 )
- {
- mtherr( "gdtr", DOMAIN );
- return( 0.0 );
- }
- return( igam( b, a * x ) );
- }
- double gdtrc( a, b, x )
- double a, b, x;
- {
- if( x < 0.0 )
- {
- mtherr( "gdtrc", DOMAIN );
- return( 0.0 );
- }
- return( igamc( b, a * x ) );
- }
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