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RE: st: RE: model for fractional data with panel data


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: RE: model for fractional data with panel data
Date   Tue, 6 Nov 2007 21:03:11 +0000 (GMT)

--- Maarten buis <maartenbuis@yahoo.co.uk> wrote:
> You can see graphs of such bimodel beta distribution in the example
> below. 

Actually that code contained a minor error in the calculation of the
constant. It does not change the shape, so the message from these
graphs doesn't change, but the correct code is below:

*-------------------- begin example ----------------
/*conventional parameterization*/
twoway function y = betaden(.5, .7, x)

/*alternative parameterization*/
local phi = 1.5
local mu = .5
local constant = exp(lngamma(`phi'))/  ///
(exp(lngamma(`mu'*`phi'))*exp(lngamma((1-`mu')*`phi')))

twoway function y = `constant'* ///
                     x^(`mu'*`phi'-1)* ///
                    (1-x)^((1-`mu')*`phi'-1)
*-------------------- end example ------------------

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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