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RE: st: RE: Hypergeometric Distribution


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Hypergeometric Distribution
Date   Wed, 22 Aug 2007 17:04:29 +0100

Apply -ln()-, -exp()- and -cond()- as needed. 

Nick 
n.j.cox@durham.ac.uk 

Marcello Pagano

> Just concerned with the accuracy.

> Nick Cox wrote:

> > Roger's posting includes what I presume is an allusion to 
> > an -egen- function _ghyper.ado that I wrote in 1999. 
> >
> > I withdrew this program as redundant some years ago, 
> > given that you can use something like 
> >
> > comb(K, k) * comb(N - K, n - k) / comb(N, n)
> >
> > wherever you want. In context N, K, n, k may be 
> > variables, scalars or placeholders for numeric
> > constants, or any mixture thereof. 
> >
> > This might need a wrapper to yield zeros where 
> > appropriate, or it might need care whenever 
> > individual terms get very large, but otherwise
> > does it raise any problems? 
> >
> > Nick 
> > n.j.cox@durham.ac.uk 
> >
> > Marcello Pagano
> >  
> >   
> >> I looked at --ssizebi-- but it seems to be focused on power 
> >> and sample 
> >> sizes.
> >>     
> >  
> > Newson, Roger B wrote:
> >
> >   
> >>> Thanks to Marcello for telling us all about this 
> recently-published
> >>> algorithm, which looks very useful. A search on
> >>>
> >>> findit hypergeometric
> >>>
> >>> in Stata finds a single reference (to a SSC package), which was
> >>> distributed as long ago as 1999. This suggests that the new 
> >>>       
> >> algorithm
> >>     
> >>> might be a good candidate for implementation in Mata by 
> >>>       
> >> Marcello, or by
> >>     
> >>> anybody else with the time and inclination to do so.
> >>>       
> >
> > Marcello Pagano
> >
> >   
> >> Does anyone have or know of Stata code to calculate the 
> Hypergeometric 
> >> Distribution accurately?
> >>
> >> See Journal of Discrete Algorithms ,  Volume 5 ,  Issue 2  
> (June 2007) 
> >> Pages: 341-347 for an article by Berkopec, HyperQuick 
> algorithm for 
> >> discrete hypergeometric distribution 
> >> 
<http://portal.acm.org/citation.cfm?id=1240586&coll=GUIDE&dl=GUIDE&CFID=
>> 27443384&CFTOKEN=80678482>.

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