From hkawakat at gmail.com  Tue Jun 19 00:33:05 2007
From: hkawakat at gmail.com (Hiroyuki Kawakatsu)
Date: Mon, 18 Jun 2007 23:33:05 +0100
Subject: [Rd] two bessel function bugs for nu<0
Message-ID: <307b90470706181533v70792d00ufc0b6e7476b085e1@mail.gmail.com>

#bug 1: besselI() for nu<0 and expon.scaled=TRUE
#tested with R-devel (2007-06-17 r41981)
x <- 2.3
nu <- -0.4
print(paste(besselI(x, nu, TRUE), "=", exp(-x)*besselI(x, nu, FALSE)))
#fix:
#$ diff bessel_i_old.c bessel_i_new.c
#57c57
#<   bessel_k(x, -alpha, expo) * ((ize == 1)? 2. : 2.*exp(-x))/M_PI
#---
#>   bessel_k(x, -alpha, expo) * ((ize == 1)? 2. : 2.*exp(-2.0*x))/M_PI

#bug 2: besselY() for nu<0
#don't know how to check in R; a few random checks against mathematica 5.2
#fix:
#$ diff bessel_y_old.c bessel_y_new.c
#55c55
#<  return(bessel_y(x, -alpha) + bessel_j(x, -alpha) * sin(-M_PI * alpha));
#---
#>  return(bessel_y(x, -alpha) * cos(M_PI * alpha) - bessel_j(x,
-alpha) * sin(M_PI * alpha));

h.
-- 
----------------------------------
Hiroyuki Kawakatsu
Business School
Dublin City University
Dublin 9, Ireland
Tel +353 (0)1 700 7496



[Rd] two bessel function bugs for nu<0
Hiroyuki Kawakatsu