R help - Aug 2006 - help with structuring random factors using lmer()

Hi,
I am an R beginner and having problems structuring my REML models. I have
a model with
y=weight
x1=time
x2=timesquared
id=individual identity
I need to structure the model such that in the random effects there is a
constant intercept for all individuals but a separate individual slope for
both x1 and x2 (a coefficient score for every individual).
m1<-lmer(weight~time+timesq+(1|id)+(timesq-1|id)+(time-1|id), data=dataset)
coef(m1)
gives me nearly what I want except there isnt an individual coefficient
score for each individual for x2.
Any suggestions very much appreciated.
Simon Pickett
s.pickett at exeter.ac.uk



Simon Pickett
PhD student
Centre For Ecology and Conservation
Tremough Campus
University of Exeter in Cornwall
TR109EZ
Tel 01326371852

probably you're looking for something like:

m1 <- lmer(weight ~ time + I(time^2) + (time + I(time^2) - 1 | id), 
data = dataset)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Simon Pickett" <S.Pickett at exeter.ac.uk>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, August 10, 2006 4:00 PM
Subject: [R] help with structuring random factors using lmer()

> Hi,
> I am an R beginner and having problems structuring my REML models. I 
> have
> a model with
> y=weight
> x1=time
> x2=timesquared
> id=individual identity
> I need to structure the model such that in the random effects there 
> is a
> constant intercept for all individuals but a separate individual 
> slope for
> both x1 and x2 (a coefficient score for every individual).
> m1<-lmer(weight~time+timesq+(1|id)+(timesq-1|id)+(time-1|id), 
> data=dataset)
> coef(m1)
> gives me nearly what I want except there isnt an individual 
> coefficient
> score for each individual for x2.
> Any suggestions very much appreciated.
> Simon Pickett
> s.pickett at exeter.ac.uk
>
>
>
> Simon Pickett
> PhD student
> Centre For Ecology and Conservation
> Tremough Campus
> University of Exeter in Cornwall
> TR109EZ
> Tel 01326371852
>
> ______________________________________________
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> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 

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