From: Fabien Lafont <lafont.fabien@gm...>  20120710 13:21:49

Thanks! The problem came from the 1/2 ! For convenience I've found the function digamma on numpy *http://docs.scipy.org/doc/scipy/reference/generated/scipy.special.psi.html But it's quite hard to find it! Maybe we can ask to add digamma in the title between parenthesis? Fabien * 2012/7/10 Damon McDougall <damon.mcdougall@...> > On Tue, Jul 10, 2012 at 08:57:24AM 0400, Benjamin Root wrote: > > On Tue, Jul 10, 2012 at 7:05 AM, Damon McDougall > > <damon.mcdougall@...>wrote: > > > > > On Tue, Jul 10, 2012 at 12:27:59PM +0200, Fabien Lafont wrote: > > > > > > > But It returns zero division error even when x is in ]0,1] > > > > > > I think it blows up at x = 0. What is the type of x in your usecase? Is > > > it an array? If x contains the element 0, you will get a zero > > > division error. You could try plotting the points explicitly: > > > > > Another problem might be the "1/2" part, which in python2.x would yield 0 > > unless one does "from __future__ import division". > > > > Ben Root > > Wow, I can't believe I didn't spot that. Nice one. > > I will update my answer according to Ben's astute observation: > > from scipy import special > from pylab import * > > x = linspace(0.5, 2.0, num=100, endpoint=True) > y = special.polygamma(0, 0.5 + 1.0/x) > plot(x, y) > show() > > Thanks Ben. > >  > Damon McDougall > http://damonisageek.com > B2.39 > Mathematics Institute > University of Warwick > Coventry > West Midlands > CV4 7AL > United Kingdom > 