[R] lme command

Joshua Wiley
2010-06-14T15:59:45Z

Hello Enrico,

One thing I notice between your two calls is that in the second you
specify data=dados, but you do not in the first.  When I try to do
something similar to your formulae using one of my longitudinal
datasets, I get the same results whether or not I put the formula for
random in a list.  Perhaps you could provide some sample data that
shows what is happening?

One other comment, rather than specifically adding each term and
interaction, you can use this shorthand:

Altura~(Idade+Idade2)*(sexo+status)

Best regards,

Josh



On Mon, Jun 14, 2010 at 6:37 AM, Enrico Colosimo <enricoc57 at gmail.com>
wrote:
> Hi,
>
> I am doing a longitudinal data set fit using lme.
> I used two forms of the lme command and I am
> getting two different outputs.
>
> FIRST
>
out<-lme(Altura~Idade+Idade2+sexo+status+Idade:sexo+Idade:status+Idade2:sexo+Idade2:status,
> random=(list(ident=~Idade+Idade2)))
>
> SECOND
>
out<-lme(Altura~Idade+Idade2+sexo+status+Idade:sexo+Idade:status+Idade2:sexo+Idade2:status,
> random= ~Idade+Idade2|ident,data=dados)
>
> I got weird results from the first one and could not understand the
> reason of it. All the results are
> exactly the same but ?the intercetp, and the two main terms sexo
> (gender) and status (treatment).
> That differences made a lot of difference in the final results.
>
> Anybody can tell me what is the differences ?between them?
> Thanks.
>
> Enrico.
>
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--
Joshua Wiley
Ph.D. Student
Health Psychology
University of California, Los Angeles