[R-sig-ME] formula objects and glmer

Christopher Chizinski chizi001 at umn.edu
Tue Feb 8 21:21:49 CET 2011

I am trying to automate running through different model subsets in
lme4 (version 0.999375-37) using glmer and storing the model output as
a list.  It runs through the sequence fine but the problem I am having
is the Formula stored in each list element has the formula object,
"form," I created rather than the specific formula.  I have looked
through several lists and can not really see where I am going wrong.
I am not sure if this is something specific to glmer or something more
basic that I am missing. Thank you for any help or direction you can
provide.

Here is an example:
set.seed(2147483647)
dat<-data.frame(event=rpois(15,
1.5),mort=c(0,0,0,0,1,1,0,0,1,0,1,0,1,0,1),X1=rnorm(15),X2=rnorm(15),X3=rnorm(15),X4=rnorm(15))
cand.vars<-data.frame(cbind(c('X1','X2'),c('X2','X4'),c('X3','X1')))
Cand.models<-list()
for(i in 1:ncol(cand.vars)){
form<-as.formula(paste("mort~",paste(cand.vars[,i],collapse
='+'),"+(1|event)"))
Cand.models[[i]]<-glmer(form,family = binomial, data = dat)
}
print(Cand.models)

# output
[]
Generalized linear mixed model fit by the Laplace approximation
Formula: form
Data: dat
AIC   BIC logLik deviance
26.29 29.12 -9.143    18.29
Random effects:
Groups Name        Variance Std.Dev.
event  (Intercept)  0        0
Number of obs: 15, groups: event, 6
Fixed effects:
Estimate Std. Error z value Pr(>|z|)
(Intercept)  -0.5155     0.5770  -0.893    0.372
X1           -0.8158     0.6354  -1.284    0.199
X2           -0.1028     0.5714  -0.180    0.857
Correlation of Fixed Effects:
(Intr) X1
X1  0.194
X2 -0.047  0.279
[]
Generalized linear mixed model fit by the Laplace approximation
Formula: form
Data: dat
AIC   BIC logLik deviance
25.76 28.59 -8.878    17.76
Random effects:
Groups Name        Variance  Std.Dev.
event  (Intercept) 3.898e-13 6.2434e-07
Number of obs: 15, groups: event, 6
Fixed effects:
Estimate Std. Error z value Pr(>|z|)
(Intercept)  -0.4947     0.5828  -0.849    0.396
X2            0.1890     0.5898   0.320    0.749
X4           -1.0695     0.8021  -1.333    0.182
Correlation of Fixed Effects:
(Intr) X2
X2 -0.175
X4  0.089 -0.167
[]
Generalized linear mixed model fit by the Laplace approximation
Formula: form
Data: dat
AIC   BIC logLik deviance
26.3 29.13  -9.15     18.3
Random effects:
Groups Name        Variance Std.Dev.
event  (Intercept)  0        0
Number of obs: 15, groups: event, 6
Fixed effects:
Estimate Std. Error z value Pr(>|z|)
(Intercept)  -0.5675     0.6611  -0.858    0.391
X3            0.1465     1.0263   0.143    0.886
X1           -0.7904     0.6103  -1.295    0.195
Correlation of Fixed Effects:
(Intr) X3
X3 -0.497
X1  0.202 -0.070