[R-sig-ME] Mixed effect logistic regression help

Christine Griffiths Christine.Griffiths at bristol.ac.uk
Wed Apr 6 13:05:31 CEST 2011

Dear Giancarlo,

Thank you for very much for your advice. I suspected that may be the case. 
Do you know if the Zelig package 
can accommodate pairing, or is simply accounting for the variance?

Many thanks in advance,

--On 05 April 2011 04:54 +0000 giancarlo <gsadoti at syr.edu> wrote:

> CJ Griffiths <Christine.Griffiths at ...> writes:
>> Dear all,
>> I want to specify a mixed conditional logistic regression to model
>> microhabitat selection, but am unsure whether my dataframe and model are
>> correct. I want to compare parameters such as wind and temperature at the
>> location of the animal (1) to a random observation, where the animal was
>> absent (0). Each Response (1/0) is thus paired by the variable Micro. To
>> account for this pairing, I specified the random effect as 1|Micro.
>> However, I repeatedly sampled 11 animals (Ind). Random effect = 1|Ind
> ...
> A little late in the response...
> To my understanding, mixed models cannot accommodate the paired 1/0
> structure of your data.  Adding micro as a mixed effect is only
> accounting for the variance in your 1/0 response among different levels
> of micro.  However, since you have an equal number of 1s and 0s for each
> level, you see zero as the variance in micro.  You need to use a
> conditional logistic model (e.g., clogit in package survival) to do what
> you want to do to accommodate the paired case/control nature of your
> samples.  However, clogit cannot accommodate the repeated sampling of
> individuals (which lmer, nlme, etc. can, but not in this case).  The only
> real application I've seen bridging these two 'worlds' is the following:
> Duchesne, T., D. Fortin, and N. Courbin. 2010. Mixed conditional logistic
> regression for habitat selection studies. Journal of Animal Ecology
> 79:548-555.
> Unfortunately, it was implemented in Matlab, so not so useful to any of
> us in R land.  Personally, I'd be very excited to see a mixed conditional
> logit package or extension developed for R, but I'm neither statistician
> nor programmer.
> Giancarlo
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Christine Griffiths
PhD student
School of Biological Sciences
University of Bristol
Woodland Road
Bristol BS8 1UG
Tel: 0117 9288918
Fax 0117 3317985
Christine.Griffiths at bristol.ac.uk

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