

Let me check that I am interpreting your data correctly. It seems that 
you have 12 sites at each of which you have a number of mated pairs. You 
have physical measurements on the male and the female of each pair and 
some environmental measurements on the sites.

Yes, that's absolutely correct.

The pairs are numbered within sites but some numbers are missing. Might 
they be the numbers corresponding to pairs that failed to fledge? I 
think maybe they should be there as well with nfledge = 0.



Actually, the missing numbers 
correspond to the rows I have removed from the original data set because
 they contained "nfledge" missing values.

'instotal' and 'weatherpc1' are measured at the 'site' level, so the 
natural way to incorporate them in a model would be through a

     (instotal + weatherpc1|site)

term.



Would it be 
(instotal+weatherpc1|site) or (instotal|site+weatherpc1|site)? According
 to the way you've written it, only "weatherpc1" seems to be in relation
 to "site". 

Surely also 'nfledge' should be at the 'pair' level ?

I think it would then be better to re-shape the data so that each row is 
a pair and, for example, 'tlength' splits into two covariates 'tlengthM' 
and 'tlengthF'.



I see the point, but what would be the difference compared to having one individual per row and sex as a factor, as it is now? 

It looks doubtful to me that a Poisson model will fit this data well, 
with or without the addition of the nfledge = 0 pairs.



Yes, the problem clearly seems to 
be in teh fact that it's a Poisson model, as assuming Gaussian errors it
 doesn't return any error message. 

I think that you should be talking more to some local statisticians 
before you attempt to fit models to this data.


Regards,  Murray



Thank you so, so much for all your suggestions. I will work on it and tell you if it worked. 



Best wishes, Iker

On 17/01/2011 9:15 a.m., Iker Vaquero Alba wrote:
>
>     Hello:
>
>     As I posted several days ago, I was trying to implement this model:
>
>
 
fledgecoltailmodel1<-lmer(nfledge~sex*briventral*inslarge*weatherpc1*tlength-sex:briventral:inslarge:weatherpc1:tlength-sex:briventral:inslarge:weatherpc1-sex:briventral:inslarge:tlength-sex:briventral:weatherpc1:tlength-sex:inslarge:weatherpc1:tlength-briventral:inslarge:weatherpc1:tlength-sex:briventral:inslarge-sex:briventral:weatherpc1-sex:briventral:tlength-sex:inslarge:weatherpc1-sex:inslarge:tlength-sex:weatherpc1:tlength-briventral:inslarge:weatherpc1-briventral:inslarge:tlength-briventral:weatherpc1:tlength-inslarge:weatherpc1:tlength+(site|pair),family=poisson)
>
>     but I got the error message:
>
>     Error in asMethod(object) : matrix is not symmetric [1,2]
>
> 
   as no one seems to know what could be the reason for that or how to 
find a solution, I was thinking that maybe I could try using another 
function. Starting with the one which seems more similar to "lmer", I 
tried with "GLMM", which I read in some post it could be taken from 
"lme4" package. However, when I try to use it (either "glmm" or "GLMM"),
 R tells me such function doesn't exist.
>
>     Do you know
 why this could be happening? Do you know of any other functions I could
 use to fit my model? I was thinking as well of "MCMCglmm", but I'm not 
sure I can apply it to my model and I don't think I'm expert enough as 
to deal with its syntax or the overdispersion problems.
>
>     I am using R 2.12.0
>
>     Thank you very much for your help!
>
>
>
>     Iker Vaquero-Alba
>
>     Centre for Ecology
> and Conservation
>
>     Daphne du Maurier
> Building
>
>     University of Exeter,
> Cornwall Campus
>
>     Treliever Road
>
>     TR10 9EZ Penryn
>
>     U.K.
>
>
>
>
>
>
>
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>
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>
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-- 
Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
Department of Statistics, University of Waikato, Hamilton, New Zealand
Email: maj@waikato.ac.nz    majorgensen@ihug.co.nz      Fax 7 838 4155
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