[R] call works with gee and yags, but not geepack

[Rolf Turner]

On 30/10/2008, at 9:08 AM, Juliet Hannah wrote:

> I have included data at the bottom of this email. It can be read in by
> highlighting the data and then using this command: dat <-
> read.table("clipboard", header = TRUE,sep="\t")
> I can obtain solutions with both of these:
>
> library(gee)
>
> fit.gee<-gee(score ~ chem + time, id=id,
> family=gaussian,corstr="exchangeable",data=dat)
>
> and
>
> library(yags)
> fit.yags <- yags(score ~ chem + time, id=id,
> family=gaussian,corstr="exchangeable",data=dat,alphainit=0.05)
>
> However, I am making a mistake with:
>
> library(geepack)
> fit.geese <- geese(score ~ chem + time, id=id,
> family=gaussian,corstr="exch",data=dat)
>
> I obtain the following error:
>
> Error in geese.fit(x, y, id, offset, soffset, w, waves, zsca, zcor,  
> corp,  :
>  nrow(zsca) and length(y) not match
>
> Could someone tell me what I have done incorrectly. Thanks for your
> time, Juliet.

I'm pretty sure this is a bug in geese(), which should be reported to  
the
maintainer of geepack.  The problem is with the treatment of missing  
values.

If looks at dim(na.omit(dat[,c("id","score","chem","time")])) one  
gets 44.
In geese.fit() zsca is set equal to matrix(1,N,1) where N is set  
equal to
length(id).  But id has length 46 whereas the response y has been  
trimmed
down to length 44 by eliminating any rows of the data where any of  
the variables
involved are missing.  Hence a problem.

The solution of the problem requires some code re-writing by the  
maintainer of geepack.

	cheers,

		Rolf Turner

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