swertie
2012-Oct-18 14:23 UTC
[R] Assessing overdispersion and using quasi model with lmer, possible?
Hello! I am trying to model data on species abundance (count data) with a poisson error distribution. I have a fixed and a random variables and thus needs a mixed model. I strongly doubt that my model is overdispersed but I don't know how to get the overdispersion parameter in a mixed model. Maybe someone can help me on this point. Secondly, it seems that quasi models cannot be implemented with the function lmer, is there an option? If not, I certainly should go to variable transformation and use a gaussian error distribution, but it is not optimal. Thank you! -- View this message in context: http://r.789695.n4.nabble.com/Assessing-overdispersion-and-using-quasi-model-with-lmer-possible-tp4646626.html Sent from the R help mailing list archive at Nabble.com.
Ben Bolker
2012-Oct-19 12:28 UTC
[R] Assessing overdispersion and using quasi model with lmer, possible?
swertie <v_coudrain <at> voila.fr> writes:> I am trying to model data on species abundance (count data) with a poisson > error distribution. I have a fixed and a random variables and thus needs a > mixed model. I strongly doubt that my model is overdispersed but I don't > know how to get the overdispersion parameter in a mixed model. Maybe someone > can help me on this point. Secondly, it seems that quasi models cannot be > implemented with the function lmer, is there an option? If not, I certainly > should go to variable transformation and use a gaussian error distribution, > but it is not optimal.You should read the section in http://glmm.wikidot.com/faq on overdispersion, and address further questions to the r-sig-mixed-models <at> r-project.org mailing list ... Ben Bolker
swertie
2012-Oct-22 07:53 UTC
[R] Assessing overdispersion and using quasi model with lmer, possible?
thank you very much -- View this message in context: http://r.789695.n4.nabble.com/Assessing-overdispersion-and-using-quasi-model-with-lmer-possible-tp4646626p4646967.html Sent from the R help mailing list archive at Nabble.com.
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