hi folks,

I believe that the construction

y ~ A + (A|B)

(where A is a categorical variable for a fixed effect and

B is a categorical variable for a random effect) will generate random

effects for all of the fixed effect coefficients. That is, in addition

fitted a systematic fixed effect coefficient for intercept and

relevant added effects of levels of A, it will fit corresponding

random coefficients for each level of B, including random intercepts,

and relevant added random effects of A, given B (i.e. for each

separate B).

Thus if you think that each family has, in addition to a different

overall mean, also has a different response to levels of A (and you

have the replication to estimate them), then you should include (A|B)

and see if it is better than simply (1|B).

Hank

On Oct 6, 2008, at 11:02 AM, Christian Ritz wrote:

> Dear Agnes,

>

> I think your model specification should look like this:

>

> YourModel1 <- lmerlmer(y ~ poptype*matingtype + (1|poptype:pop) + (1|

> poptype:fam),

> data = ...)

>

>

> The "1" in front of "|" refers to models that are random intercepts

> models as opposed to

> general random coefficients models in which case "1" would need to

> be replaced by a

> variable that is quantitative. So, the "(poptype|/pop/fam)"

> construction is definitely not

> relevant to your problem, unless "poptype" is a quantitative

> variable...

>

> The combined factor "poptype:pop" corresponds to the factor pop, but

> taking the nesting

> structure into account. Similar for the construction "poptype:fam".

>

>> From the summary output of the lmer() fit you should be able to

>> check whether or not the

> correct number of groups are used for these random factors.

>

> Kind regards

> Christian

>

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Dr. Hank Stevens, Associate Professor

338 Pearson Hall

Botany Department

Miami University

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Office: (513) 529-4206

Lab: (513) 529-4262

FAX: (513) 529-4243

http://www.cas.muohio.edu/~stevenmh/http://www.cas.muohio.edu/ecologyhttp://www.muohio.edu/botany/"If the stars should appear one night in a thousand years, how would men

believe and adore." -Ralph Waldo Emerson, writer and philosopher

(1803-1882)

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https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.