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Diffstat (limited to 'libm/ldouble/btdtrl.c')
-rw-r--r-- | libm/ldouble/btdtrl.c | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/libm/ldouble/btdtrl.c b/libm/ldouble/btdtrl.c new file mode 100644 index 000000000..cbc4515da --- /dev/null +++ b/libm/ldouble/btdtrl.c @@ -0,0 +1,68 @@ + +/* btdtrl.c + * + * Beta distribution + * + * + * + * SYNOPSIS: + * + * long double a, b, x, y, btdtrl(); + * + * y = btdtrl( a, b, x ); + * + * + * + * DESCRIPTION: + * + * Returns the area from zero to x under the beta density + * function: + * + * + * x + * - - + * | (a+b) | | a-1 b-1 + * P(x) = ---------- | t (1-t) dt + * - - | | + * | (a) | (b) - + * 0 + * + * + * The mean value of this distribution is a/(a+b). The variance + * is ab/[(a+b)^2 (a+b+1)]. + * + * This function is identical to the incomplete beta integral + * function, incbetl(a, b, x). + * + * The complemented function is + * + * 1 - P(1-x) = incbetl( b, a, x ); + * + * + * ACCURACY: + * + * See incbetl.c. + * + */ + +/* btdtrl() */ + + +/* +Cephes Math Library Release 2.0: April, 1987 +Copyright 1984, 1995 by Stephen L. Moshier +Direct inquiries to 30 Frost Street, Cambridge, MA 02140 +*/ +#include <math.h> +#ifdef ANSIPROT +extern long double incbetl ( long double, long double, long double ); +#else +long double incbetl(); +#endif + +long double btdtrl( a, b, x ) +long double a, b, x; +{ + +return( incbetl( a, b, x ) ); +} |