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I am using the get.models command from package MuMIn in R Studio. I am working off my supervisor's code, and he has used the subset command throughout his code.

I don't understand what the subset = 2, or subset = 3, refers to and I can't find it anywhere in any instructions for MuMIn. I understand that subset = 1)[[1]] is to get the top model.

e.g.

fm.2018.ITD <- lm(ITD.2018 ~ scale(temp_max_s.2018)*scale(slope) +
                 scale(precip_dry_month_s.2018)*scale(slope) +
                 scale(ndvi.pchange.2018)*scale(slope) + 
                 scale(aspect) + scale(hillshade) + scale(mass_fl_pa) + 
scale(EUNIS_div),
               data=bee.env.ITD.change)
summary(fm.2018.ITD)
dd.ITD.2018.slope <- dredge(fm.2018.ITD)
subset(dd.ITD.2018.slope, delta < 2)
ITD.2018.slope.best <- get.models(dd.ITD.2018.slope, subset = 2)[[1]]
summary(ITD.2018.slope.best)
Evie McCloughan
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1 Answers1

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the delta is used to subset a set of models based on a criteria. If your models (obtained from the dredge function) are ranked according to their AIC value, using delta < 2 will select the best model (based on AIC), the second best and so on until the AIC difference between the last selected model and the next one is larger than 2.

Their is no argument specified in the dredge function so by default models are sorted on their AIC value.

glagla
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