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warnings ranef and design of a binomial model

3 messages · Robert ESPESSER, Douglas Bates

Original
Robert ESPESSER
# 
Dear R users,

I have a question about model design.
One group of 20 subjects run the A experiment, with 17 binary responses by subject.
An other group of 20 subjects run the 2 experiments B and C, with 20 binary responses by subject, 
for both of the 2 experiment.

I want to study the effect of the  factor "expe"  
I tried this covariance model:
mod.glmer <-  glmer( vd ~ dlms*expe +(1|subject) +(0+dlms|subject) , 
              family=binomial, ....)

where:
dlms is a numeric factor (-2,-1,0, 1,2)
expe is a 3 levels factor , coding the experiment (A or B or C)

vd is the success/fail matrix.

The model with a random slope is clearly better than an intercept-only model.

the results look plausible, ranef(mod.glmer, postVar=T) was OK for the
Intercept, but failed
to compute the postvar of the random slope , with these warnings:
1: In min(x): no argument found for min; Inf is returned
It's the same for max.

I'm  suspecting  that my model is perhaps badly designed , concerning the 
unbalanced repartition of the subjects across the experiments. Is it correct ?

Thanks for any comments or suggestions.

####
sessionInfo()  is:
R version 2.7.2

lme4_0.999375-26
Matrix_0.999375-13


Robert Espesser
Laboratoire Parole et Langage  UMR 6057, CNRS
29 Av. Robert Schuman  13621 AIX    (FRANCE)
Tel: +33 (0)4 42 95 36 26   Fax: +33 (0)4 42 95 37 88
http://www.lpl-aix.fr
Douglas Bates
# 
I think we would need at least the output from traceback() to see
where the error is occurring.  Better yet would be to have access to
the data so we could try out the model fits.  Sometimes these errors
show up deep inside another computation.  Does

ranef(mod.glmer)

produce a result?  I'm trying to decide if the problem is in the
postVar part or in the ranef part.

On Wed, Sep 10, 2008 at 5:29 AM, Robert ESPESSER
<Robert.Espesser at lpl-aix.fr> wrote:
Robert ESPESSER
# 
The warning messages are output by dotplot(ranef() ).
ranef(xxx ,postVar=T) by  itself does not output any warning messages. 

The models:
modG.glmer <- glmer( vd ~ dlms*expe  +(dlms|subject) ,family=binomial, ....)
modI.glmer <- glmer( vd ~ dlms*expe  +(1|subject) ,family=binomial, ....)
modS.glmer <- glmer( vd ~ dlms*expe  +(0+dlms|subject) ,family=binomial, ....)

have their dotplot(ranef()) OK. 

The problem is only with the model:
modIS.glmer <-  glmer( vd ~ dlms*expe +(1|subject) +(0+dlms|subject) ,family=binomial, ....)

ranef(modIS.glmer)-> rr.glmer
$subject

Warning messages:
1: In min(x) : aucun argument trouv? pour min ; Inf est renvoy?
2: In max(x) : aucun argument pour max ; -Inf est renvoy?

traceback() returns nothing :
2: bar(2)
1: foo(2)
(because I have tested it with the example in ?traceback)

In addition, how can I extract the postVar component in a ranef object ?
Dr Bates, in case you need the data , do I have attach them in a private mail to you ?

here is the complete sessionInfo():
R version 2.7.2 (2008-08-25) 
i386-pc-mingw32 

locale:
LC_COLLATE=French_France.1252;LC_CTYPE=French_France.1252;LC_MONETARY=French_France.1252;LC_NUMERIC=C;LC_TIME=French_France.1252

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base     

other attached packages:
[1] lme4_0.999375-26   Matrix_0.999375-13 lattice_0.17-13   

loaded via a namespace (and not attached):
[1] grid_2.7.2  nlme_3.1-89