R devel - Apr 1997 - R-alpha: Bug & Patch in dbeta.c (0.50 - PreR 7)

dbeta(1, a,b)  would return 1 instead of 0.

Here is the patch for  ..../src/math/dbeta.c :

--- dbeta.c~	Sun Nov 24 23:43:10 1996
+++ dbeta.c	Tue Apr 15 21:25:30 1997
@@ -23,9 +23,7 @@
 {
 	if (a <= 0.0 || b <= 0.0)
 		DOMAIN_ERROR;
-	if (x <= 0)
+	if (x <= 0 || x >= 1.0)
 		return 0.0;
-	if (x >= 1.0)
-		return 1.0;
 	return MATH_CHECK(pow(x, a - 1) * pow(1.0 - x, b - 1.0) / beta(a, b));
 }
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On Tue, 15 Apr 1997, Martin Maechler wrote:
> dbeta(1, a,b)  would return 1 instead of 0.
Shouldn't it be 1 for b=1, Inf for b<1 and 0 for b>1 at x=1 (and
similar
behaviour at x=0)?

ie 
double dbeta(double x, double a, double b)
{
        if (a <= 0.0 || b <= 0.0)
                DOMAIN_ERROR;
        if (x < 0)
                return 0.0;
        if (x > 1.0)
                return 0.0;
        return MATH_CHECK(pow(x, a - 1) * pow(1.0 - x, b - 1.0) / beta(a,
b));
}




Thomas Lumley
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