[R] Warning messages: not meaningful for factors

[Dieter Menne]

Dr Shrink wrote:
> 
> I need to include the repeated structure in our data set object,
> recall.sums.df, before using gls function.
> Thus I used groupedData.
> But I encountered error messages which may mean '*' is not not meaningful
> factor.
> 

I know that when reading Pinheiro/Bates one has the expression that
groupedData is required, but I always found that concept more confusing than
helpful (and it has been abandoned in nlm4). Things work much more
transparent without grouped data.

I suggest that you first the numeric data to factors, e.g.

recall.sums.df$subj = as.factor(recall.sums.df$subj)

and then try again without using grouped data. However, it looks too me that
you might be better of with lme anyway, probably with random= ~1|subj. gls
is a very useful and underused tool, but probably not for this data set.
I also suggest that you start getting the syntax right with + instead of *
first. You model could easily be strongly underspecified, which also lead to
nasty error messages.

Dieter





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