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Re: st: nonlinear growth curve in xtmixed


From   David Airey <david.airey@vanderbilt.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: nonlinear growth curve in xtmixed
Date   Fri, 12 Dec 2008 21:27:10 -0600

Stata does not yet do nonlinear mixed models, of the kinds you are talking about.

It would be nice if we could have these models, because then I could have random effects for pharmacodynamic models, like dose response models.

-Dave

On Dec 12, 2008, at 5:29 PM, josemaria wrote:

Dear Stas and Maarten:
thank you for your kindness. But it seems that neither -xtmelogit- nor -xtmepoisson- nor gllamm do apply, because the response variable is not binary or count. For example, for -xtmelogit- the output is odds ratio. Rabe-Hesketh presents growth curve only in linear and quadratic polynomial forms. I am interested in continuous variables, as kg, or m, or bmi (body mass index), that moves through time according to a logistic curve, but not a curve of probability from 0 to 1. Singer & Willett use an iterative maximum likelihood procedure proposed by Pinheiro & Bates (Mixed-Effects Models in S and S- Plus,Springer, 2000, pages 337-347); the response variable in Pinheiro & Bates example is the trunk circumference (in mm) of trees, and time is day. Each tree is measured seven times.
José Maria
By the way, I am not able to write anything in Mata!

Jose Maria Pacheco de Souza, Professor Titular (aposentado)
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904  -  S. Paulo/SP - Brasil
fones (11)3061-7747; (11)3768-8612
fax (11)3714-2403
www.fsp.usp.br/~jmpsouza
----- Original Message ----- From: "Stas Kolenikov" <skolenik@gmail.com >
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, December 12, 2008 6:54 PM
Subject: Re: st: nonlinear growth curve in xtmixed


As of version 10, Stata provides -xtmelogit- and -xtmepoisson- for
logistic and Poisson models, respectively. I believe Singer & Willett
only talk about logistic models there, right? You can say those are
nonlinear models since the mean functions are nonlinear in x's; to me
those are extensions of generalized linear model, and hence there is
at least some linear flavor to them. PROC NLMIXED can fit some crazy
models with direct integration of the random effects (as far as I
know), and full functionality of that is not available in Stata (at
least in the easily available commands; you can write anything you
want in Mata!)

On 12/12/08, josemaria <jmpsouza@usp.br> wrote:
Dear Statalisters:
Judith D. Singer and John B. Willet, in their book "Applied Longitudinal
Analysis", Oxford University Press, 2003, present, in pages 225-232,
analysis for nonlinear growth curve using the PROC NLMIXED of SAS, and explain that, at the time of writing the book, Stata did not have yet the
same capability.
This is also informed at the end of the page: "Stata Textbook Examples Applied Longitudinal Data Analysis: Modeling Change and Event Occurrence
by Judith D. Singer and John B. Willett
Chapter 6: Modeling Discontinuous and Nonlinear Change",
site
http://www.ats.ucla.edu/stat/stata/examples/alda/chapter6 :
 "Table 6.6 on page 231.

* Skipped these for now. Stata does not yet do nonlinear mixed models." Is
it possible now to do such analysis in Stata?
Than you for any orientation.
José Maria

Jose Maria Pacheco de Souza, Professor Titular (aposentado)
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904  -  S. Paulo/SP - Brasil
fones (11)3061-7747; (11)3768-8612
fax (11)3714-2403
www.fsp.usp.br/~jmpsouza
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--
Stas Kolenikov, also found at http://stas.kolenikov.name
Small print: I use this email account for mailing lists only.

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