[ADMB Users] ADMB versus R

dave fournier davef at otter-rsch.com
Thu Nov 8 08:59:42 PST 2012

I think you a re missing the point.

This all began because a guy asked a question about a seeming 
contradiction in
his model fits on the R list. He got the usual runaround about his data 
not being good
enough or whatever.

Now after years of watching this stuff my general opinion is that people 
who trust
the R gurus for information more or less deserve what they get.

However in this case glmmadmb is something that I am partly responsible 
for so
I react when I think someone is getting bad advice.  I took a fair 
amount of time
and R pain to recreate his analysis and discovered that glmmadmb is not 
doing what one
might assume in this case.

I quickly hacked together what I assume is the model the guy wanted and 
it did
produce a better fit as one would expect. However the improvement was 
not significant.

Then Ben modified the R code to produce what he assumed was the correct 
and posted the results, noting that they were different from mine with the
implication that I must be doing something wrong.

However he never checked the log-likelihood for his new model. It is a 
lot worse
than the original user's LL so the model is not what he thinks it is.

I ran my model on the glmmadmb.dat file that Ben's model produced and 
got the
same LL as he got.  I agree with him that the design matrix Z appears to be
correct, but there must be something wrong with the dat file.  I wonder
if it is the II's.

Anyway this is neither convenient or quick and I have more interesting 
things to work on.

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