summaryrefslogtreecommitdiff
path: root/libm/ldouble/btdtrl.c
diff options
context:
space:
mode:
Diffstat (limited to 'libm/ldouble/btdtrl.c')
-rw-r--r--libm/ldouble/btdtrl.c68
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 ) );
+}