Thanks a lot Joshua. Regards, Indrajit
On Tue, Apr 30, 2013 at 1:13 PM, Joshua Wiley <jwiley.ps...@gmail.com> wrote: > Hi Indrajit, > > In your first SAS code, change to type=un. cs imposes the (somewhat > dubious) assumption that the variance of both the intercept and slope are > equal. If you are using lme4, all random effects in a single block (e.g., > (1 + month | batch) the 1 = intercept and month = random slope) will have an > unstructured (or freely estimated) variance covariance matrix. > > Cheers, > > Josh > > > > On Mon, Apr 29, 2013 at 11:26 PM, Indrajit Sengupta > <indrajitsg2...@gmail.com> wrote: >> >> Hi All, >> >> I am trying to shift from running mixed models in SAS using PROC MIXED >> to using lme4 package in R. In trying to match the coefficients of R >> output to that of SAS output, I came across this problem. >> >> The dataset I am using is this one: >> >> >> http://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_mixed_sect034.htm >> >> If I run the following code: >> >> proc mixed data=rc method=ML covtest; >> class Batch; >> model Y = Month / s; >> random Int Month / type=cs sub=Batch s; >> run; >> >> The Fixed effect coefficients match with that of R. But the random >> effect does not. Here is the R code: >> >> rc <- read.table('rc.csv', sep = ',', header=T, na.strings=".") >> >> m1 <- lmer(formula = Y ~ Month + (Month|Batch), data = rc, REML = F) >> >> summary(m1) >> >> fixef(m1) >> >> ranef(m1) >> >> But if I change the SAS code as follows: >> >> proc mixed data=rc method=ML covtest; >> class Batch; >> model Y = Month / s; >> random Int / type=cs sub=Batch s; >> run; >> >> and the R code as follows: >> >> m2 <- lmer(formula = Y ~ Month + (1|Batch), data = rc, REML = F) >> >> summary(m2) >> >> fixef(m2) >> >> ranef(m2) >> >> both fixed and random effect coefficients match. I am unable to >> understand this discrepancy. Am I wrongly specifying the model in the >> first case? >> >> It would be helpful if someone can throw some light on this. >> >> Regards, >> Indrajit >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. > > > > > -- > Joshua Wiley > Ph.D. Student, Health Psychology > University of California, Los Angeles > http://joshuawiley.com/ > Senior Analyst - Elkhart Group Ltd. > http://elkhartgroup.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
