john.maindonald at anu.edu.au
Wed Dec 1 04:21:11 CET 1999
Berwin Turlach wrote -
> > >>>>> "JM" == John Maindonald <john.maindonald at anu.edu.au> writes:
> JM> At 08:02 30/11/99 +0000, Prof Brian D Ripley wrote:
> >> On Tue, 30 Nov 1999, spoon <spoon at hilbert.maths.utas.edu.au> wrote:
> >>> Hi,
> >>> Is this a bug or do I just not understand model.tables?
> >>> [...]
> >>> Or am I just completely misinterpreting something basic?
> >> Basically, yes. This is an incompletely replicated design, and d and e
> >> occur on different litters.
> >> The results are identical to the S-PLUS original. I think you are
> >> probably looking for what dummy.coef gives you.
> >> [...]
> JM> So what is it that model.tables() gives?
> Good question, in R (0.65.1) the documentation of model.tables says:
> The implementation is incomplete, and only the simpler
> cases have been tested thoroughly.
Simon and I had noted that. As S-PLUS has no such warning, perhaps
the discussion should be taking place on s-news.
> JM> S-PLUS says they are estimates. Of what? These are not the
> JM> marginal means of the fitted values, ignoring other factors. Do
> JM> they mean anything at all? The issue of unbalance does not
> JM> arise here.
> The documentation in R also states that
> For `type = "effects"' give tables of the coefficients
> for each term, optionally with standard errors.
> For `type = "means"' give tables of the mean response
> for each combinations of levels of the factors in a
> Hence, my understanding would be that if `type="means"' is specified
> the marginal means of the observations ignoring other factors is
> given. But this doesn't seem to be the case, at least not with an
> unbalanced design. You can use either your dreamed up example or the
> data that spoon has posted.
On the usual definitions of `balance' both in my example and
Simon's example treatments are `balanced" over blocks (or litters).
John Maindonald email : john.maindonald at anu.edu.au
Statistical Consulting Unit, phone : (6249)3998
c/o CMA, SMS, fax : (6249)5549
John Dedman Mathematical Sciences Building
Australian National University
Canberra ACT 0200
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