[R] Repeated measures using lme

From: Tom Cohen <tom.cohen78_at_yahoo.se>
Date: Thu, 06 Mar 2008 10:51:46 +0100 (CET)

Dear list,    

  I am trying to do a repeated analysis using lme in R and a little bit unsure if I have set up the right statement. The problem is the IL6 (interleukin 6) was measured 5 times on each individual in each of 6 companies. The hypotheses are to see whether there is a relationship between IL6 and the total dust in each of the companies and if there is any change in IL6 across time points. So the fixed effects are total dust, company and random effects is individual. The model would be like this    

  lme(IL6~ dust + time*company, random=~time|individual,

                        correlation=corAR1(form=~time|individual), data=dat)

   with time as a repeated measure.    

   the analysis in SAS would be    

  proc mixed data=dat;
  class time individual company;
  model IL6=dust company time company*time;   repeated time/Sub=individual(company) type=AR(1) r rcorr;   random individual;

  lsmeans company time company*time/slice=time;   run;    

  Am I writing the right code in R that would give me the same results if doing the analysis in SAS. Also is there any command in R that does the same thing as SLICE in SAS does, to test when in time there is difference between companies?    

  Thanks for any help,

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