[Scipy-tickets] [SciPy] #1713: documentation for scipy.stats.distributions.gamma incorrect

SciPy Trac scipy-tickets@scipy....
Tue Jul 31 03:35:40 CDT 2012


#1713: documentation for scipy.stats.distributions.gamma incorrect
-------------------------+--------------------------------------------------
 Reporter:  jisk attema  |       Owner:  somebody   
     Type:  defect       |      Status:  new        
 Priority:  low          |   Milestone:  Unscheduled
Component:  Other        |     Version:  0.10.0     
 Keywords:               |  
-------------------------+--------------------------------------------------
 the documentation for the gamma distribution is incorrect.
 see for example http://en.wikipedia.org/wiki/Gamma_distribution

 Calculating by hand

 >>> rv = distributions.gamma(1, scale=0.5 )
 >>> print math.exp(-2) * 2
 0.270670566473

 >>> print rv.pdf(1)
 0.270670566473

 shows the implementation is correct.


 The text:

     The probability density function for `gamma` is::

         gamma.pdf(x, a) = (lambda*x)**(a-1) * exp(-lambda*x) / gamma(a)


 Should be:


     The probability density function for `gamma` is::

         gamma.pdf(x, a) = lambda**a x**(a-1) * exp(-lambda*x) / gamma(a)

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1713>
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