[R-sig-ME] [R] understanding I() in lmer formula

Don Cohen don-r-help at isis.cs3-inc.com
Sat Jun 17 18:29:35 CEST 2017

Ben Bolker writes:
 > For the level of detail you're getting into, it would be a really good
 > idea to read the paper that accompanies the lme4 package:
 > vignette("lmer",package="lme4") .  This goes into a lot of detail
 > about the theory and data structures ...

gives me
 Warning message: 
 vignette 'lmer' not found  

Is this the same as 
https://cran.r-project.org/web/packages/lme4/vignettes/lmer.pdf ?

I think that's the same one that I was having trouble with before
and gave up around eqn 15.
Although, I had the impression that it (looks like eqn 14) was
describing what I expected and asked about in a previous message,
namely paying only once for each group and then once for each data
point within the group.

Are you saying that the vignette link above actually answers the
questions in this last message about how to compute the loglik of
the model?  It doesn't look to me like it will.  
I view my current line of questions (and I have many more, but am
trying to resist bombarding you with all at once) as a way to get
the background I'll need to get through that paper.

In fact, one of my questions when I read that paper was what 
correlated vs uncorrelated intercept and slope meant - I didn't 
see any explanation.  I think that Emmanuel Curis has now explained
that, but I'm still trying to check my understanding.

Since I'm writing anyway, let me indulge in one more question about
the formulas.  Since (x|g) means correlated intercept and slope for
x, does (x+y|g) include a separate correlation between x slope and
y slope?  That is, the cost of specifying a group would involve a
3 dimensional normal distribution over intercept,x,y ?

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