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Re: st: RE: Growth curve with -gllamm- (any way to get peak velocity and height?)


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Growth curve with -gllamm- (any way to get peak velocity and height?)
Date   Fri, 10 Aug 2007 19:06:55 +0100 (BST)

--- Joseph Wagner <joseph.wagner@wright.edu> wrote:
> 2. In terms of functional forms, by including a quadratic term our 
> simple model (using a measurement, age, and the square of age fits
> well.

The growth is just the first derivative with respect to age, so you can
just create a variable containing the growth and use -sum- to see the
maximum.

gen growth = _b[age] + 2*_b[age2]*age
sum growth

Notice that it is a charateristic of your parameterization that the
maximum growth will occur at the edges (when the subjects are youngest
and oldest), and I am not sure if that is desirable if you are
explicitly interested in finding out when the growth is fastest.

Hope this helps,
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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