I am also quite new to lme4 myself, so I'll just add one thing to Toby's
earlier answer.

On Tue, Feb 1, 2011 at 5:14 PM, Colin Wahl <biowahl@gmail.com> wrote:

> Dear r-sig-mixed-models List,
>
> [snip]



> Secondarily: I have read a few times that "wshed/stream" is interchangeable
> with  "wshed:stream" which is a meaningless interaction. Also I've seen
> that
> random effects are specified as (a|b) where a is a covariate and b is a
> grouping factor. Does having 1 as a covariate simply specifying an
> intercept
> of 1? What is the purpose of placing a factor in the place of 1 as a
> covariate? OR is there a nice complete summary tutorial that I've missed.
>
A specification of (1|b) means that the model is fit with a random effect
for each level of b (simple scalar random effect). The "a" in (a|b) is a
correlated random effect along with "b", with both an intercept and slope.
You can also make them uncorrelated, with slope only for a.

The draft of Prof. Doug Bate's book covers many useful basics on lmer, and
is where I learned most of mine.
http://lme4.r-forge.r-project.org/book/

HTH
George


>
> I'm looking forward to hearing any comments.
>
> Thank you,
> --
> Colin Wahl
> Department of Biology
> Western Washington University
> Bellingham, WA 98225
> ph: 360-391-9881
>
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