Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
(801) 408-8111
> -----Original Message-----
> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] On Behalf Of Ben Bolker
> Sent: Friday, May 02, 2008 7:36 AM
> To: r-help at stat.math.ethz.ch
> Subject: Re: [R] Data manipulation for random intercept GLMM
>
> Giovanni Petris <GPetris <at> uark.edu> writes:
>
> > > ## Example: Ratings of prime minister (Agresti, Table
> 12.1, p.494)
> > > rating <- matrix(c(794, 86, 150, 570), 2, 2)
> > > dimnames(rating) <- list(First = c("approve", "disapprove"),
> > + Second = c("approve", "disapprove"))
> > > rating
> > Second
> > First approve disapprove
> > approve 794 150
> > disapprove 86 570
> >
> [snip]
> >
> > > approval <- factor(c("Approve", "Disapprove"),
> > + levels = c("Disapprove", "Approve"))
> > > survey <- factor(c("First", "Second")) tmp <-
> data.frame(approval =
> > > unlist(expand.grid(approval, approval)),
> > + survey = rep(survey, each = 4))
> > > rat.df <- cbind(tmp[rep(1:8, rep(rating, 2)), ],
> > + id = factor(rep(1:sum(rating), 2)))
> > > row.names(rat.df) <- NULL
> >
> > That does the job, since now I can call lmer:
> >
> > > m1 <- lmer(approval ~ survey + (1 | id), family =
> binomial, data =
> > > rat.df,
> > + method = "Laplace")
> >
> [snip]
>
> >
> > Consider also that the next simplest example is the following, in
> > which there are three items on a questionnaire and gender
> is included
> > in the model:
> >
> > > ### Example: Support for legalizing abortion (Agresti,
> Table 10.13,
> > > p.441) legalize <- matrix(c(342, 440, 26, 25, 6, 14, 21,
> 18, 11, 14,
> > + 32, 47, 19, 22, 356, 457), nr = 2)
> > > dimnames(legalize) <- list(Gender = c("Male", "Female"),
> > + Three = c(111, 112, 211, 212, 121,
> > + 122, 221, 222))
> > > legalize
> > Three
> > Gender 111 112 211 212 121 122 221 222
> > Male 342 26 6 21 11 32 19 356
> > Female 440 25 14 18 14 47 22 457
> >
> > (Here '111' means (Yes, Yes, Yes) on the three items, etc.)
> >
> > How can I tranform elegantly this table into a dataframe that I can
> > feed to lmer?
> >
>
> I would like to know the answers to this as well. I
> thought I was going to be able to get away with
> as.data.frame.table() [which is handy and underappreciated],
> but it doesn't expand counts.
> I hope you get an elegant solution: in the meantime, I
> guess my advice is to try to write a reasonably general (if
> not necessarily absolutely elegant) function that you can
> supply your students with.
> If they have an expand.table() function, they won't care how
> complex it is internally ...
>
> Ben Bolker
>
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