[R] add1() alternative

[brunosm]

Hi,

I'm trying to build a hierarchical logistic regression model with lme4
package, but I have a problem on selecting the variables to include in this
model.

In a simple logistic regression, using Forward selection, i use a likelihood
ratio test to check which variables i should include in the model, using the
function add1().

The problem is that this function doesn't work with the hierarchical model
that i'm trying to achieve.

Example:

model<- glmer(y ~ (1 | group)+x+sex+age, family = binomial("logit"), data =
db)
add1(model, db, test="Chisq")
Error: $ operator not defined for this S4 class

I know that the drop1() function works fine to do a backward selection, but
the problem is that i have 40 variables, and which time i use drop1() i have
to wait a loooooong time to get a result...

Is there any alternative to add1()? I mean, i don't want to use
anova(model1,model2) because i would have to do all the models by hand...


Thanks a lot guys,

Bruno



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