[R] error in nlme
bates at stat.wisc.edu
Thu Sep 13 00:56:25 CEST 2001
Setzer.Woodrow at epamail.epa.gov writes:
> I'm getting an error from nlme that has me stymied. I have a data set
> ,'mydata', with variables: AChE, Dose, sex, set, and mrid; 'set' and 'mrid'
> indicate two levels of nesting, with 'set' nested within 'mrid'. I want to
> fit the model:
> mod <- nlme(AChE ~ Cexp(Dose, A, B, m), data=mydata, fixed = A+B+M~sex,
> random=A+B+m~sex | mrid/set, weights=varPower(fixed=1))
> (mydata has over 1000 records, so I won't reproduce it here).
> When I run this, I get the error:
> Error: dim<- length of dims do not match the length of object
> It turns out the error is being thrown by the statement:
> dim(work$pdFactor) <- dim(pdMatrix(nlmeSt$reStruct[]))
> Browse> length(work$pdFactor)
>  72
> Browse> dim(pdMatrix(nlmeSt$reStruct[]))
>  6 6
> It looks like work$pdFactor contains information about both levels of
> nesting, which is being ignored.
> Does someone have an idea for a fix (or am I abusing nlme)?
You're not abusing nlme - it is supposed to be able to do that but the
R version doesn't.
The original S code for nlme had to be modified for R and the
modifications for the case of nested grouping factors were getting
very complicated. I eventually punted and modified it so it would
work with a single grouping factor only (that's the reStruct[] in
People have claimed that this did work in R at one time. I'm not
sure. I don't remember fixing it myself.
Fixing this would take a non-trivial amount of time and given the
number of things already on my "To Do" list I can't predict when I
will be able to look at it.
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