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R-squared for generalized linear mixed-effects models

This function has been completely rewritten and included in the piecewiseSEM package as sem.model.fits. See updates here: https://github.com/jslefche/piecewiseSEM/

Description:

Implementation of Schielzeth and Nakagawa's R2 for generalized linear mixed effects models in R. This function improves on the r.squaredGLMM function in the MuMIn package by incorporting different link functions for GLMERs and also returning other useful information, such as the model specification, and additional fit criteria in the form of AIC values.

For more information, see:

Nakagawa, Shinichi, and Holger Schielzeth. "A general and simple method for obtaining R2 from 
generalized linear mixed‐effects models." Methods in Ecology and Evolution 4.2 (2013): 133-142.

Johnson, Paul C.D. "Extension of Nakagawa & Schielzeth's R2GLMM to random slopes models." Methods in
Ecology and Evolution.

Version: 0.2-4 (2014-07-10)

Author: Jon Lefcheck jslefche@vims.edu & Juan Sebastian Casallas

Original blog post: http://jonlefcheck.net/2013/03/13/r2-for-linear-mixed-effects-models/

####WARNING: Calculation of nested random effects in lme objects still in beta!!

Examples

Generate a mock dataset

set.seed(4)
data <- data.frame(y=rnorm(100, 5, 10), y.binom=rbinom(100, 1, 0.5), y.poisson=rpois(100, 5))
data <- cbind(data, 
              data.frame(fixed1=data$y+c(runif(50, 0, 5),runif(50, 10, 50)),
                         fixed2=c("Treatment1", "Treatment2"),
                         rand1=LETTERS[1:2],
                         rand2=rep(LETTERS[23:26],each=25)) )

lme4

library(lme4)
#Linear model
mod0 <- lm(y ~ fixed1, data)
#Linear mixed effects model
mod1 <- lmer(y ~ fixed1 + (1|rand2/rand1), data)
rsquared.glmm(mod1)
mod1.1 <- lmer(y ~ fixed1 + (fixed1|rand2/rand1), data)
mod2 <- lmer(y ~ fixed1 + fixed2 + (1|rand2/rand1), data)
rsquared.glmm(list(mod0, mod1, mod1.1, mod2))
#Generalized linear mixed effects model (binomial)
mod3 <- glmer(y.binom ~ fixed1*fixed2 + (1|rand2/rand1), family="binomial", data)
mod3.prob <- update(mod3, family = binomial(link = "probit"))
rsquared.glmm(list(mod3, mod3.prob))
#Generalized linear mixed effects model (poisson)
mod4 <- glmer(y.poisson ~ fixed1*fixed2 + (1|rand2/rand1), family="poisson", data)
mod4.sqrt <- update(mod4, family = poisson(link = "sqrt"))
rsquared.glmm(list(mod4, mod4.sqrt))
#Get values for all kinds of models
(lme4.models <- rsquared.glmm(list(mod0, mod1, mod1.1, mod2, mod3, mod3.prob, mod4, mod4.sqrt)))

Compare output to MuMIn::r.squaredGLMM

MuMIn::r.squaredGLMM is similar to rsquared.glmm but returns less information and cannot handle different kinds of link functions:

library(MuMIn)
(mumin.models <- do.call(rbind, lapply(list(mod0, mod1, mod1.1, mod2, mod3, mod3.prob, mod4, 
mod4.sqrt), r.squaredGLMM)))

blme

blme extends lme4, but yields different coefficients for random and fixed effects, which could explain the differences between their conditional r-squared values.

library(blme)
#Linear mixed effects model
blme.mod1 <- blmer(y ~ fixed1 + (1|rand2/rand1), data)
blme.mod1.1 <- blmer(y ~ fixed1 + (fixed1|rand2/rand1), data)
blme.mod2 <- blmer(y ~ fixed1 + fixed2 + (1|rand2/rand1), data)
#Generalized linear mixed effects model (binomial)
blme.mod3 <- bglmer(y.binom ~ fixed1*fixed2 + (1|rand2/rand1), family="binomial", data)
blme.mod3.prob <- update(blme.mod3, family = binomial(link = "probit"))
#Generalized linear mixed effects model (poisson)
blme.mod4 <- bglmer(y.poisson ~ fixed1*fixed2 + (1|rand2/rand1), family="poisson", data)
blme.mod4.sqrt <- update(blme.mod4, family = poisson(link = "sqrt"))
#Get values for all kinds of models
(blme.models <- rsquared.glmm(list(mod0, blme.mod1, blme.mod1.1, blme.mod2, blme.mod3, blme.mod3.prob,
blme.mod4,blme.mod4.sqrt)))
# blme models yield better conditional r-squared values
all.equal(lme4.models[-(1:2)], blme.models[-(1:2)])

lmerTest

lmerTest::lmer extends lme4::lmer, but their random and mixed effects coefficients are the same.

# Try with lmerTest package -- output should be the same as above
library(lmerTest)
#Linear mixed effects model
lmerTest.mod1 <- lmer(y ~ fixed1 + (1|rand2/rand1), data)
lmerTest.mod2 <- lmer(y ~ fixed1 + fixed2 + (1|rand2/rand1), data)
rsquared.glmm(list(mod0, lmerTest.mod1, lmerTest.mod2))
(lmerTest.models <- rsquared.glmm(list(mod0, lmerTest.mod1, lmerTest.mod2)))
# Same results
all.equal(lme4.models[1:3, -(1:3)], lmerTest.models[,-(1:3)])

lme

nlme::lme and lme4::lmer yield very similar r-squared values.

library(nlme)
lme.mod1 <- lme(y ~ fixed1, random=~1|rand2/rand1, data)
#Change to old optimizer to solve convergence issueslme4.models2[2:4, -(1:3)]
lme.mod1.1 <- lme(y ~ fixed1, random=~fixed1|rand2/rand1, control = lmeControl(opt = "optim"), data) 
lme.mod2 <- lme(y ~ fixed1 + fixed2, random=~1|rand2/rand1, data)
(lme.models <- rsquared.glmm(list(lme.mod1, lme.mod1.1, lme.mod2)))
# Compare to lme4 models, minor differences
all.equal(lme4.models2[2:4, -(1:3)], lme.models[,-(1:3)], tol = 1e-4)