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Re: st: boundary constraints within nl


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: boundary constraints within nl
Date   Fri, 6 Jun 2008 18:43:11 +0100 (BST)

--- Marc Keuschnigg <Marc.Keuschnigg@soziologie.uni-muenchen.de> wrote:
> I am estimating non linear least squares models (nl) using equations 
> like: nl (y =  ({a}+{b}* x) * (1-x)).
> My question is, how do I impose parameter restrictions like a >=0 and
> b >=0?
> I could log-transform the parameters, but I don't know how to do it 
> technically within the nl command.

nl (y =  (exp({a})+exp({b})* x) * (1-x))

-- Maarten

-----------------------------------------
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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