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

[Joseph Wagner <joseph.wagner@wright.edu>]

1. We want to fit the individuals together.
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.


Nick Cox wrote:

> This fills in some of the background science. 
> It seems to leave unclear: 
> 1. Quite how demographic data are to be related to 
> individuals. More broadly, whether you intend fitting
> individuals separately or together. My guess is 
> the latter, but it helps to spell things out. 
> 2. Whether you have specific discipline-approved 
> growth curve functional forms in mind or are going
> to use more general methods. 
> Even if you answer these questions, I will not be 
> able to add very much more, if anything, but others 
> might start tuning in and give you specific advice. 
> Nick 
> n.j.cox@durham.ac.uk 
> Joseph Wagner
>  
>   
> > The research involves craniofacial skeletal growth measurements.  The 
> > data consist of several angle measurements at junctions between bones 
> > and length measurements of specific areas of bone.  We have 
> > demographic 
> > data as well.  We get measurements (using x-rays) from individuals 
> > annually over their lifetime.  We want to know at which point the 
> > greatest rate of growth occurs and the peak growth velocity for 
> > individuals and the mean for our entire sample.  We also want to know 
> > the rate of bone recession in older persons.
> >
> > Nick Cox wrote:
> >     
> > > It isn't obvious from this information alone that -gllamm-
> > > is the only or even the best way to do it. That said, 
> > > there will be ways to get key properties of fitted 
> > > growth curves, even if only numerically. Quite how 
> > > will depend on what you do precisely, so better answers
> > > might depend on further information. 
> > > Nick 
> > > n.j.cox@durham.ac.uk 
> > > Joseph Wagner
> > >  
> > >   
> > >       
> > > > I have data composed of yearly jaw xray measurements over a 20 year
> > > > period.  I wish to do some growth curve analyses of these 
> > > > data so I plan
> > > > to use -gllamm- but I was wondering, is there a way to get 
> > > > the mean peak
> > > > velocity and the mean peak height of the growth curve?
> > > >         
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--
Joseph H. Wagner, M.P.H.
Lifespan Health Research Center
Wright State University Boonshoft School of Medicine
3171 Research Blvd.
Kettering, OH  45420-4014

(937) 775-1494 (LHRC office)
(937) 775-1456 (fax)

joseph.wagner@wright.edu

Visit the Lifespan Health Research Center Home Page at:
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