Dear R-users,

I'm currently having trouble with the implementation of a groupedData object in the lme() function.

Executing the following function
applyScalingSimp <- function(input.population)
{
        ## GA is a time value
        varInOrder <- c("GA","weight","grouping","sex")
        modelVar <- c("GA_","VARI1","id","v51026")
        names(modelVar) <- varInOrder

        ## The following re-expresses the time in the spline basis.
        GASpline <- rcspline.eval(input.population[,modelVar["GA"]],
knots=quantile(input.population[,modelVar["GA"]], probs=qVec<-c(0.05,0.275,0.5,0.725,0.95),na.rm=TRUE),
                                    inclx=TRUE)

colnames(GASpline) <- paste("GA",head(seq_along(qVec),n=-1),sep="")
        input.population <- cbind(input.population,GASpline)

lmeFormula <- as.formula(paste("VARI1", "~", modelVar["sex"],"+ (", paste(colnames(GASpline),sep="",collapse="+"), ")|id")) groupFrame <- groupedData(formula = lmeFormula, data = input.population)

        lme.output <- lme(  fixed=groupFrame,
random=do.call(what="pdDiag",args=list(form=as.formula(paste("~",paste(colnames(GASpline),collapse="+"),sep="")))),
                            correlation = corSymm,
                            na.action=na.omit)

        return(lme.output)
}
with the following data.frame object as a value for the input.population argument
"GA_" "VARI1" "id" "v51026"
123 7.28824594963692 5 1
185 9.97279896947955 5 1
231 11.4784464688259 5 1
262 12.3480880103964 5 1
277 12.7415557997424 5 1
131 7.52808268709084 38 1
176 9.5429893459525 38 1
232 11.4704437962050 38 1
258 12.1768098655929 38 1
280 12.5830142986889 38 1
126 7.3457418485436 41 2
177 9.66889759453008 41 2
232 11.4729189241886 41 2
261 12.1974400314058 41 2
292 12.2546939619415 41 2
124 7.17697081721814 56 2
174 9.40475505947726 56 2
230 11.4940807273184 56 2
250 11.9731637779112 56 2
294 12.8907335176616 56 2
yields the following error message
Error in inherits(x, "data.frame") : object 'groupFrame' not found
However, groupFrame does exist (as shown by using the debug() function).

Can anyone here offer an explanation as to why this might be occurring?

Just in case you might want it...
_ platform i386-pc-mingw32 arch i386 os mingw32 system i386, mingw32 status major 2 minor 9.0 year 2009 month 04 day 17 svn rev 48333 language R version.string R version 2.9.0 (2009-04-17)

Cheers,

--
*Luc Villandré*
/Biostatistician
McGill University Health Center -
Montreal Children's Hospital Research Institute/

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