The lme4 package is the de facto package for linear mixed models. Its syntax has become a standard in the industry and most researchers working with applied linear models use it. As we have seen with many techniques so far, the problem with it is that it can be impacted greatly by outliers. Even a minor contamination causes major estimation problems.
Robust mixed effects models with robustlmm
Getting ready
The lme4 and robustlmm packages are needed for this recipe. They can be installed using install.packages().
How to do it...
In this recipe, we will use the robustlmm...
