[Rd] besselI inaccurate for negative integer order (PR#13556)

From: <Jerry.Lewis_at_biogenidec.com>
Date: Thu, 26 Feb 2009 16:15:11 +0100 (CET)

Full_Name: Jerry W. Lewis
Version: 2.8.1
OS: Windows XP Professional
Submission from: (NULL) (

It should be the case that
  besselI(x,-nu) == besselI(x,nu) == besselI(x,abs(nu)) for integer nu, yet R currently can return ridiculous values when nu is a negative integer.

For instance, besselI(9.6,-44) returns -234626490 instead of the correct value of 5.9041042646307223e-25, while besselI(9.6,44) gives essentially machine accuracy.

This is more than an idle mathematical curiosity, since one consequence is that dskellam in the VGAM package can return values <0 or >1.

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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Thu 26 Feb 2009 - 19:23:02 GMT

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