Error in besselJ(pi/2, 1E-15)?

Leo Mada via R-help <[email protected]> Sun, 28 Dec 2025 16:28:42 +0000

Newsgroups	gmane.comp.lang.r.general
Message-ID	<DBAP192MB0956A03DB297C16C857A695084BEA@DBAP192MB0956.EURP192.PROD.OUTLOOK.COM>

Dear R-Users,

besselJ(pi/2, 0)
# 0.4720012
besselJ(pi/2, 1E-14)
# 0.4720012
besselJ(pi/2, 1E-15)
# 4.720012e+14

There seems to be an error in besselJ(pi/2, eps), where eps is close to 0; although besselJ(pi/2, 0) is well behaved.

I am not an expert in the field - but it doesn't seem right.

Sincerely,

Leonard


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