[R] syntax for a 3-level nlme model

Christine Calmes ccalmes at buffalo.edu
Thu Nov 15 17:01:03 CET 2007

I am writing to verify the syntax that I am using to test a 3-level 
> model with a random intercept at the second level (participant in my 
> model) versus a model with a random slope and intercept at this 
> level.  Specifically, I am testing a 3 level model in which time 
> (WEEK) is nested in participants (PARTICIP) and participants are 
> nested in dyads (DYADID). The goal is to examine how an 
> style (CORUMTO) one week predicts changes in depression the 
> week (BDIAFTER) controlling for levels of depression (BDI) from the 
> previous week.
> I want to verify that the following syntax would be appropriate 
> for modeling a random intercept and fixed slope at the participant 
> level and a random slope and intercept at the participant level
> both<-lme(BDIAFTER~BDI+WEEK+CORUMTO, random=list(DYADID=~1,  
> PARTICIP=~CORUMTO), data=weeklydata)
> Also, when modeling a random slope and intercept at the participant 
> level, I receive output, and I also receive the following error 
> message…
> Warning message
> Fewer observations than random effects in all level 2 groups
> I was wondering what this error message means and if it may be 
> suggesting that the results after the summary statement are
> incorrect.
> I also want to verify that the following syntax is appropriate for
> modeling just a random intercept (and a fixed slope) at the dyad
> and participant levels…
> intercept<-lme(BDIAFTER~BDI+WEEK+CORUMTO, random=list(DYADID=~1, 
> PARTICIP=~1), data=weeklydata)
> Any advice you can give would be much appreciated.
> Thank you for your time.
> Sincerely,
> Christine Calmes
> Christine Calmes, M.A.
> Doctoral Candidate, Clinical Psychology
> University at Buffalo: The State University at New York
> Department of Psychology; Park Hall
> North Campus
> Buffalo NY, 14260

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