R help - Aug 2008 - A repeated measures, linear mixed model (lme) WITHOUT random effects...

Hello,

I am trying to fit a repeated measures linear mixed model (using lme) 
but I don't want to include any random effects. I'm having trouble (even
after consulting Pinheiro & Bates 2000) figuring out how to specify the 
repeated measure without including it in the specification of a random 
effect.

My data consist of repeated "counts" in "plots" that I wish
to model as
a function of "habitat". This attempt:

          model<-lme(count~habitat-1,data=dataframe,method="ML")

doesn't consider the repeated nature of my counts (i.e., that there are 
multiple rows in my dataframe for each plot). I know how to 
include"plot" as a random effect, but I don't wish to do that, and
I
can't see how to include it without doing so.

I'll appreciate any help you can provide.

Thanks, Mark

Mark

lme is for models with random effects. You need to consult gls() and the
corresponding discussion of this function in Pinhiero and Bates. BTW, if you
have no random effects it is no longer a mixed model.


-----Original Message-----
From: r-help-bounces@r-project.org on behalf of Mark Na
Sent: Mon 8/25/2008 7:59 PM
To: R-help@stat.math.ethz.ch
Subject: [R] A repeated measures,linear mixed model (lme) WITHOUT random
effects...
 
Hello,

I am trying to fit a repeated measures linear mixed model (using lme) 
but I don't want to include any random effects. I'm having trouble (even
after consulting Pinheiro & Bates 2000) figuring out how to specify the 
repeated measure without including it in the specification of a random 
effect.

My data consist of repeated "counts" in "plots" that I wish
to model as
a function of "habitat". This attempt:

          model<-lme(count~habitat-1,data=dataframe,method="ML")

doesn't consider the repeated nature of my counts (i.e., that there are 
multiple rows in my dataframe for each plot). I know how to 
include"plot" as a random effect, but I don't wish to do that, and
I
can't see how to include it without doing so.

I'll appreciate any help you can provide.

Thanks, Mark

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