[SciPy-user] Where do I send bug reports ? Bug in function iv

Mark Bakker markbak@gmail....
Fri Sep 21 03:24:40 CDT 2007


Hello -

I couldn't find a place to send bug reports.

I submitted this to the list a couple of weeks ago, but I haven't had a
response yet, and I don't want it to get lost (I really hope somebody knows
how to fix it)

It seems that the modified Bessel function iv returns incorrect values for
large argument.

iv(0,100) gives 5.72185663838e+041

while the equivalent

jv(0,complex(0,100))
(1.07375170713e+042+0j )

This latter results is the correct answer, as verified in Abramowitz and
Stegun, Table 9.11, Page 428. Using the jv is a work-around, but this should
probably be fixed. The two results start to deviate for arguments over about
50, with jv giving the correct answer.

On a related note, there are implementations for Bessel functions of integer
order (jn, kn) but not for the modified Bessel function In. I guess this is
because the function would be called 'in', but it would be nice to have a
special function for integer order, and I am pretty sure they are around.

Thanks, Mark
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