? Error in stepAIC??

["Hunsicker, Lawrence" <lawrence-hunsicker@uiowa.edu>]

Good morning, all:

I have tried to run stepAIC on a glmmPQL model.  The first function (glmmPQL) works fine.  But when I run the stepAIC function, I get the error:

 ‘Object “tt” not found’ 

ScrMiss.glmm<-glmmPQL(fixed = Scr.missing ~ Sexe + Age1 + Age.miss + Ethnie + HistoryDiabete + DurDiab + DurDiab.miss

        + Retinopathie + PiedDiabetique + Hypertension + DurBP + DurBP.miss + SBP1 + SBP.miss + DBP1 + DBP.miss

        + AntecedentTabac + Hyperlipidemie + LVH + CAD + MI + CHF + Stroke + PVD + MedicamentDiabete + NoBPMeds

        + Diuretique + ACEInhibitor + Calciumchannelblockers + ARBs + Statins + OtherLipid

        + NoAnticoag + Aspirin + OtherAnticoagulant + NumberBPClasses

        , random = ~1|Region/Pays/Center, family = binomial(link=logit),data="" = F, niter=15)

minmod.glmm <- stepAIC(ScrMiss.glmm, direction = "both")

> minmod.glmm <- stepAIC(ScrMiss.glmm, direction = "both")

Start:  AIC= 126349.7

 Scr.missing ~ Sexe + Age1 + Age.miss + Ethnie + HistoryDiabete + DurDiab + DurDiab.miss + Retinopathie + 

        PiedDiabetique + Hypertension + DurBP + DurBP.miss + SBP1 + SBP.miss + DBP1 + DBP.miss + AntecedentTabac +

        Hyperlipidemie + LVH + CAD + MI + CHF + Stroke + PVD + MedicamentDiabete + NoBPMeds + Diuretique + 

        ACEInhibitor + Calciumchannelblockers + ARBs + Statins + OtherLipid + NoAnticoag + Aspirin + 

        OtherAnticoagulant + NumberBPClasses

Problem in switch(data.class(object),: Object "tt" not found

Use traceback() to see the call stack

I checked to see whether the glmmPQL object (ScrMiss.glmm) had the “extract.AIC()” method, and it does. 

What am I doing wrong this time?

As always, my thanks to anyone that can get me on the right track again.

Larry Hunsicker