When I change it, my outcome also changes a lot, so I need to be able to understand how to set my limits.Ĭan someone help me? This is my first question on stackoverflow, so please bear with me :) I'm happy to provide more information if needed.Dredging is one of our key tasks, both to maintain adequate water depth for boaters and as part of our work to improve water quality. Specifying limits as m.min and m.max is allowed for backward compatibility.' Unfortunately, I don't understand how to define the number of terms in a single model, also after reading 'Subsetting'. In the R help page, it says ' optionally, the limits c(lower, upper) for the number of terms in a single model (excluding the intercept). However, this code is from a different project and I don't understand how the m.lim was defined (neither does my colleague). Summary(get.models(dredge_CO2, subset = 1)]) Nullmodel_CO2 <- MuMIn.nullFitRE(CO2.null)ĭredge_CO2 <- dredge(CO2.null, m.lim = c(0,5), rank = 'AIC', extra =list(R2 = function(x) ))ĭredge_CO2 # this is the most parsimonious (=best) model, thus the one I will use + (1|Chamber) + (1|Date), data= data_CO2_noNA, REML = FALSE) I have received the following code from a colleague, where I build a saturated model with all explanatory variables: CO2.null <- lmer(log(CO2_flux) ~ Temperature + Moisture + Inclination I thus run the models separately for 'Inclination' and 'Distance' (the following code shows Inclination). I cannot include both inclination and distance into the code, and because I only have 4 distances, I can also not include it as a random effect. Chambers are a tool to measure GHG, and we had 16 chambers in 4 distances from a stream (= 4x4 replicates), with differing topography (inclination).

My fixed effects are soil temperature, soil moisture and topography, whereas my random effects are chambers and date. According to my hypotheses, I look at each GHG seperately with mixed models including random effects.

I am working on a large dataset looking at effects of soil temperature, soil moisture and topography on greenhouse gases (GHG CO2, CH4 and N2O).

Dredge define