rlme4random-effectsmixed-models

How to get coefficients and their confidence intervals in mixed effects models?


In lm and glm models, I use functions coef and confint to achieve the goal:

m = lm(resp ~ 0 + var1 + var1:var2) # var1 categorical, var2 continuous
coef(m)
confint(m)

Now I added random effect to the model - used mixed effects models using lmer function from lme4 package. But then, functions coef and confint do not work any more for me!

> mix1 = lmer(resp ~ 0 + var1 + var1:var2 + (1|var3)) 
                                      # var1, var3 categorical, var2 continuous
> coef(mix1)
Error in coef(mix1) : unable to align random and fixed effects
> confint(mix1)
Error: $ operator not defined for this S4 class

I tried to google and use docs but with no result. Please point me in the right direction.

EDIT: I was also thinking whether this question fits more to https://stats.stackexchange.com/ but I consider it more technical than statistical, so I concluded it fits best here (SO)... what do you think?


Solution

  • I'm going to add a bit here. If m is a fitted (g)lmer model (most of these work for lme too):

    If you prefer to use broom.mixed:

    You can also get confidence intervals by parametric bootstrap (method="boot"), which is considerably slower but more accurate in some circumstances.