[R-sig-ME] Modeling correlation structure in mixed models
Robert A LaBudde
ral at lcfltd.com
Sat Jun 27 01:34:08 CEST 2009
West et al. Linear Mixed Models. Chapman & Hall.
This text uses SAS, SPSS, HLM and R to set up and solve a variety of
hierarchical mixed models. The text uses 'nlme' exclusively, but the
related website has 'lme4' equivalent scripts.
At 06:42 PM 6/26/2009, Phillip Chapman wrote:
>I have been trying to learn mixed models in R by reading the books
>by Pinheiro and Bates; Faraway (both linear models books); and
>Crawley (R Book), but I would appreciate some guidance from the more
>experience R users. (I have a fair amount of experience with mixed
>models in SAS.)
>1. Is there another (other than the above) suggested reference for
>understanding the workings of the nlme and lme4 libraries?
>2. Is it the case that lme accepts correlated structures ONLY in the
>error term? I have problems in which I would like model random
>effects (such as year) using a random term with an autocorrelated
>structure. In SAS I use options to the "repeated" statement to add
>correlation structure to the error term, and I use options to the
>"random" statement to give correlation structure to the other random
>effects. I haven't found anything in lme or lmer that allows me to
>specify correlated random effects. gee only allows correlation
>structure in the error term and does not allow random effects.
>3. All of the examples of random effects in lme seem to have nested
>error structures. Is it the case that lme does not allow crossed
>random effects? lmer allows much more flexible specification of
>random effects, but I don't see anything that allows correlated
>Thanks in advance,
>R-sig-mixed-models at r-project.org mailing list
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral at lcfltd.com
Least Cost Formulations, Ltd. URL: http://lcfltd.com/
824 Timberlake Drive Tel: 757-467-0954
Virginia Beach, VA 23464-3239 Fax: 757-467-2947
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