Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: -gammafit-, -pgamma- and -qgamma- packages on SSC


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: -gammafit-, -pgamma- and -qgamma- packages on SSC
Date   Wed, 12 Nov 2003 22:12:21 -0000

Thanks to Kit Baum, various packages to do 
with fitting two-parameter gamma distributions 
have been added to or revised on SSC. 

To clarify a possible source of confusion, 
let me note that _none_ of these packages 
has any connection with the official 
Stata command -gamma-. -gamma- was added 
in Stata 6.0. As of Stata 8.* it is now 
undocumented, but still very present. It is 
written for three-parameter gamma distributions, 
especially as the basis of survival models. 

gammafit (new package, written by Nicholas J. Cox 
and Stephen P. Jenkins) 
=======================

-gammafit- fits a two-parameter gamma distribution 
with a shape parameter and a scale parameter, 
optionally as dependent on covariates. Stata 8 
is required. 

Also included in this package is -gamma4-, which 
also fits a two-parameter gamma distribution, 
although to a single variable only. That may 
be used in Stata 4 through 7. 

(Note: -gamma4- was previously called -gamma-. 
It predated official Stata's -gamma-, but 
because of Stata's thoroughly sensible -adopath- 
rules, only users of Stata 4 or Stata 5 could 
both install it and run it without problem. 
It seems high time to rename it, as is now 
done. The SSC package -gamma- is simultaneously 
abolished.) 

pgamma (revised, author NJC) 
============================

-pgamma- produces a probability plot compared with a
two-parameter gamma distribution with a shape parameter
and a scale parameter. Fitting is done quietly by -gammafit-, 
which should be installed separately. These programs 
all require Stata 8. 

Also included is the previous version, now renamed
as -pgamma4-, which may be used in Stata 4 through 7. 
Estimation may be performed using -gamma4-, 
available as part of the -gammafit- package. 

qgamma (revised, author NJC) 
============================

-qgamma- plots the quantiles of a variable against 
the quantiles of a two-parameter gamma distribution 
with a shape parameter and a scale parameter. 
Fitting is done quietly by -gammafit-, which should 
be installed separately. These programs all require 
Stata 8. 

Also included is the previous version, now renamed
as -qgamma4-, which may be used in Stata 4 through 7. 
Estimation may be performed using -gamma4-, 
available as part of the -gammafit- package. 

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

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index