Hi! I am trying to know which habitat variables most affect bird counts in a radius of 100m. I obtained bird counts in 2751 spatial points, and measured percentage of 21 habitat variables in these points. I applied a mixed model using the "lmer" function to these data, but I do not know how to select the best model using AIC here. Is there a way to do this automatically with R? Thank you for any help! Silvia - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Por favor, para comunicarte conmigo utiliza preferentemente la dirección silviadiazfernandez@gmail.com. En enero de 2011 dejará de funcionar la actual silvia.diaz@uclm.es. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Silvia Díaz Fernández Tlf.: (+34) 926 295 450 ext. 3377 Fax: (+34) 926 295 451 silviadiazfernandez@gmail.com Instituto de Investigación en Recursos Cinegéticos (IREC) Ronda de Toledo s/n 13005 Ciudad Real España http://www.uclm.es/IREC - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - [[alternative HTML version deleted]]
Hi! I am trying to know which habitat variables most affect bird counts in a radius of 100m. I obtained bird counts in 2751 spatial points, and measured percentage of 21 habitat variables in these points. I am applying a mixed model using the ?lmer? function to the data, but I do not know how to select the best model using AIC here. Is there a way to do this automatically with R? Thank you for any help! Silvia -- View this message in context: http://r.789695.n4.nabble.com/Minimum-AIC-mixed-model-selection-tp3039410p3039410.html Sent from the R help mailing list archive at Nabble.com.
SILVIA DIAZ FERNANDEZ <Silvia.Diaz <at> uclm.es> writes:> > Hi! > > I am trying to know which habitat variables most affect > bird counts in a radius of 100m. I obtained bird > counts in 2751 spatial points, and measured percentage of > 21 habitat variables in these points. > > I applied a mixed model using the "lmer" function to these data, > but I do not know how to select the best model > using AIC here. Is there a way to do this automatically with R? >See the MuMIn package, and the "dredge" function. e.g.: library(MuMIn) library(lme4) example(lmer) dredge(fm1) **however**: if you have 21 habitat variables and want to consider all subsets of main effects only, you will have something like 2^21 approx. 2 million models to consider. Probably a bad idea. I would strongly recommend that you consider some sort of dimension reduction (e.g. take the first few PCAs of the habitat predictors) first.