[SciPy-User] Strange behavior of sph_jn

ZIEGLER Yann (ETU EOT) yann.ziegler@etu.unistra...
Tue Apr 10 08:49:50 CDT 2012


Hi,

It seems that the bug I have with sph_jn for some values is due to scipy
itself. I finded someone having the same kind of trouble on 
projects.scipy.org/scipy (the website seems to have some technical problems
at this time).

If anyone is interested in it, here is the solution I have finded to
circumvent this bug :

Using the definition of Spherical Bessel function involving Bessel function
(http://functions.wolfram.com/Bessel-TypeFunctions/SphericalBesselJ/02/),
I wrote -- nothing extraordinary, this is a 2-lines function -- my own
SphericalBessel function (naive but seemingly correct) for positive or
negative order n and complex argument z : 

import numpy as np
from scipy.special import jn

def SphericalBessel(n,z):

   zsqrt = np.sqrt(np.abs(z)) * np.exp(np.angle(z)/2)
    
   return np.sqrt(np.pi/2) / zsqrt * jn(n+0.5, z)

Yann



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