[R] glmmPQL and variance structure

From: Patrick Giraudoux <patrick.giraudoux_at_univ-fcomte.fr>
Date: Wed 28 Dec 2005 - 04:44:59 EST


Dear listers,

glmmPQL (package MASS) is given to work by repeated call to lme. In the classical outputs glmmPQL the Variance Structure is given as " fixed weights, Formula: ~invwt". The script shows that the function varFixed() is used, though the place where 'invwt' is defined remains unclear to me. I wonder if there is an easy way to specify another variance structure (eg varPower, etc..), preferably using an lme object of the varFunc classes ? Some trials show that the 'weights' argument of glmmPQL is just the same as in glm (which is clearly stated in the help) and I wonder actually, if not a nonsense, how to pass eg a 'weights' arguments as used in lme (eg weights=varPower()) to specify a variance function (in the same way as a correlation structure can be passed easy).

Thanks in advance for any hint,

Patrick



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