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st: update betafit

From   Maarten buis <>
To   stata list <>
Subject   st: update betafit
Date   Fri, 30 Oct 2009 09:02:57 -0700 (PDT)

Thanks to Kit Baum a update of the -betafit- package is now available on 
SSC. This package is written Nick Cox, Stephen Jenkins and me, and fits a 
beta distribution to your data. This is a flexible distribution for 
variables that are boundend between zero and one. An important application 
are regression-like analyses when the depedent variable is a proportion. 

This update improved the likelihood function such that it is more 
numerically stable. In simulations the old likelihood function had trouble 
in case of strong bi-modality of the dependent variable when using the 
alternative parameterization. This update fixes that problem. (For those 
who are interested in the technical details: I replaced occurences of 
1-invlogit(xb) by invlogit(-xb) ) 

To update this package when it is already installed on your machine type 
in Stata -ssc install betafit- or -adoupdate, update-. To install 
-betafit- type in Stata: -scc install betafit-. 

-- Maarten

Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen


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