On Tue, 14 Sep 2004, Chris Solomon wrote: > Hello- > > I'm trying to do some repeated measures ANOVAs. In the past, using SAS, > I have used the framework outlined in Littell et al.'s "SAS System for > Mixed Models", using the REPEATED statement in PROC MIXED to model > variation across time within an experimental unit. SAS allows you to > specify different within-unit covariance structures (e.g., compound > symmetric, AR(1), etc.) to determine the best model. > > I'm having trouble figuring out how to do a similar analysis in R. While > 'lme' will let you choose the class of correlation structure to use, it > seems to require that you specify this structure rather than using the > data to estimate the covariance matrix. For example, it seems that to > specify 'corAR1' as the correlation structure, you have to pick a value > for rho, the autoregressive parameter.
Why does `it seems'? Your information is incorrect. > So, my question: is there a way to tell 'lme' what sort of covariance > structure you'd like to model, and then let the function estimate the > covariances? That is the default. Take a look at the examples in Venables & Ripley or Pinheiro & Bates (as recommended in the posting guide and the FAQ). > Or, alternatively, is there a better way to go about this > sort of repeated measures analysis in R? I've exhausted my available R > resources and done a pretty good search of the help archives without > finding a clear answer. Did you look at the references in the FAQ? > Chris Solomon > Center for Limnology > Univ. of Wisconsin You do know where the maintainer of the nlme package works, don't you? I am sure your University library has a copy or two of Pinheiro & Bates! -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
