Alternatives to lmer
Hi Iker, you don't give us information about your data set or the number of levels of your factors. Although you have removed some of the interactions from the model it would seem that you are trying to estimate a very large number of parameters in the fixed part of the model. I would guess that many would be unidentifiable. Any software that you might try could have trouble fitting this model. Why don't you start off more slowly with main effects only and then use try() to identify interactions that would be worth adding to your model? Murray Jorgensen
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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Dr Murray Jorgensen http://www.stats.waikato.ac.nz/Staff/maj.html Department of Statistics, University of Waikato, Hamilton, New Zealand Email: maj at waikato.ac.nz majorgensen at ihug.co.nz Fax 7 838 4155 Phone +64 7 838 4773 wk Home +64 7 825 0441 Mobile 021 0200 8350