[SciPy-User] polylogarithm?

Johann Cohen-Tanugi johann.cohentanugi@gmail....
Fri Sep 23 08:21:12 CDT 2011


hi there, in working on this I need to deal with zeta function, 
especially for complex numbers. Hopefully I will manage to implement it 
based on what is in mpmath (kudos the developers of this impressive 
package!), but I came around a more mundane behavior that maybe can be 
improved :

In [493]: special.zeta(3,1)
Out[493]: 1.202056903159594

In [494]: special.zetac(3)+1
Out[494]: 1.2020569031595942

In [495]: special.zetac(-3)+1
Out[495]: 0.0083333333333333037

In [496]: special.zeta(-3,1)
Out[496]: nan

In [497]: mpmath.zeta(-3)
Out[497]: mpf('0.0083333333333333332')

in plain words,
zetac(z) knows how to eat negative arguments, but not zeta(z,1).... Is 
there a reason why special.zeta does not default to 1+special.zetac for 
s=1? This would make the behavior of the 2 functions more identical.

best,
Johann

On 09/15/2011 08:09 AM, Johann Cohen-Tanugi wrote:
> hi there, any chance for a polylog implementation in scipy.special? I
> know it is there in mpmath, but I thought I would ask anyway.
> best,
> Johann
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