predict.glmmPQL Problem

I have found a similar problem when constructing formulae and passing
them to glmmPQL. My solution was to use do.call(glmmPQL,...). See ?do.call.

terms(model2)

Spencer Graves wrote:
	  Please try again after upgrading to the versions of R and MASS.

	  If you still have a problem, PLEASE do read the posting guide!
"www.R-project.org/posting-guide.html" before you submit another post.
Most of the people who donate their time to answer questions on this
listserve are more likely to answer a question if it is simple and
completely self contained -- including a very brief toy example that
they can copy from an email into R and reproduce the problem.  If they
can't do that, they are less likely to understand your question and
therefore less likely to produce a useful answer -- and less likely to
bother to even read carefully your question.

	  hope this helps,
	  spencer graves

rsubcriber wrote:

Dear all,

for a cross-validation I have to use predict.glmmPQL() , where the
formula of
the corresponding glmmPQL call is not given explicitly, but constructed
using as.formula.
However, this does not work as expected:

x1<-rnorm(100); x2<-rbinom(100,3,0.5); y<-rpois(100,2)
mydata<-data.frame(x1,x2,y)

library(MASS)
# works as expected
model1<-glmmPQL(y~x1, ~1 | factor(x2), family=poisson, data=mydata)
predict(model1, newdata=mydata, type="response")

f<-as.formula(paste("y", "~","x1"))
# predict does not work:
# Error in mCall[["fixed"]][-2] : object is not subsettable
model2<-glmmPQL(f, ~1 | factor(x2), family=poisson, data=mydata)
predict(model2, newdata=mydata, type="response")

Has anyone an idea what goes wrong?
I am using R 2.0.1 under Windows 2000.

Thanks,
Anneke