search for: varran

Greetings, 1) Is there a nice way of extracting the variance estimates from an lme fit? They don't seem to be part of the lme object. 2) In a series of simulations, I am finding that with ML fitting one of my random effect variances is sometimes being estimated as essentially zero with massive CI instead of the finite value it should have, whilst using REML I get the expected value. I guess

...o do some bootstrapping and get an estimate of the V-C matrix of epsilon_i. But I haven't been able to figure out how to weight the observations properly in an lme() call. Some searching of the archives led me to a 2004 posting (courtesy of Dave Atkins) of two functions written by Jose: varRan and varWithin. This gives me some hope (a good deal of hope, actually), but I can't understand the arguments or how to use these functions. Here's the posting: http://tolstoy.newcastle.edu.au/R/help/04/04/0245.html Any hints would be greatly appreciated. Thanks, Todd