[Scipy-tickets] [SciPy] #750: Bessel function jn(3, 4) inaccurate

SciPy scipy-tickets@scipy....
Wed Oct 8 20:33:09 CDT 2008


#750: Bessel function jn(3, 4) inaccurate
--------------------+-------------------------------------------------------
 Reporter:  ilan    |       Owner:  somebody
     Type:  defect  |      Status:  new     
 Priority:  normal  |   Milestone:          
Component:  Other   |     Version:          
 Severity:  normal  |    Keywords:          
--------------------+-------------------------------------------------------
 The Bessel function special.jn(3,4) in inaccurate.
 Across different operating systems (OSX, Windows, Linux) and
 different version of scipy recent being 0.7.0.dev4673,
 the following little program

 {{{
 from numpy import linspace
 import scipy.special

 N = 5
 x = linspace(3.999, 4.001, N)
 y = scipy.special.jn(3, x)

 for i in xrange(N):
     print "%10.6f  %10.6f" % (x[i], y[i])
 }}}

 gives this output

 {{{
   3.999000    0.430130
   3.999500    0.430151
   4.000000    0.397150
   4.000500    0.430192
   4.001000    0.430213
 }}}

 The value at x=4.0 is incorrect, as the Bessel function does not have a
 kink in this region.

-- 
Ticket URL: <http://scipy.org/scipy/scipy/ticket/750>
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