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