Using lme() for split plot
That's a good example with a couple levels of nesting (similar to the examples in the other book), but they still only have one factor, 'Variety', nested in each block. Am I missing something? Should I make up a psuedofactor with four levels to code my two two-level factors?
On Thu, May 7, 2009 at 5:46 PM, Rub?n Roa-Ureta <rroa at udec.cl> wrote:
Joshua Stults wrote:
Hi, I'm trying to figure out how to use lme() for analyzing a split-plot experiment. ?I've been looking at the examples from the 'R Book', those are nested but with only one factor at the whole-plot level, my test is 2^2 at the whole-plot level, with a single many level factor at the sub-plot level. ?My question is about properly specifying the random effects part of the model, lme( y ~ block + a*b*poly(c, n), random=~ ? ) Where 'a' and 'b' are my two level whole-plot factors and 'c' is the many level sub-plot factor. ?I'm not sure what to use to get the right error terms. ?Do I use two error terms: random = ~ 1 | block/a + 1 | block/b or one: random = ~ 1 | block/a*b or something else entirely? ?I haven't been able to find any relevant examples on Google. Thanks for any suggestions/pointers.
Have you checked Pinheiro and Bates 2004 Mixed-effects models in S and S-PLUS? They have a split-plot example starting on p. 45. Rub?n
Joshua Stults Website: http://j-stults.blogspot.com