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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 19:16:30 +0100

There are many answers to this, but dinner 
supervenes. 

If you push hard enough, and show why it is 
needed, either StataCorp or a user 
will write a program for this. 

The evidence since 1999 has been that such 
a program is not needed. 

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

Marcello Pagano
 
> Why buy Stata if you are expected to do all this for yourself?

 
> Nick Cox wrote:
> > 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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