Help! I have convergence warnings

After all the hard work of collecting the data, thinking about appropriate models, formatting the data, you are finally running your model, this is it you are going to get the long awaited results and BOUM you get out such kind of message: ## Warning in checkConv(attr(opt, "derivs"), opt$par, ctrl = ## control$checkConv, : Model …

Adding group-level predictors in GLMM using lme4

Sometime I happen to be wrong, this is one of these instance. The issue: a colleague measured individual plant growth and measured light irradiation received by each individual, the plants where in groups of 10 individuals and he measured soil parameters at the group-level. To analyze the effect of light on plant growth while controlling …

Interpreting random effects in linear mixed-effect models

Recently I had more and more trouble to find topics for stats-orientated posts, fortunately a recent question from a reader gave me the idea for this one. In this post I will explain how to interpret the random effects from linear mixed-effect models fitted with lmer (package lme4). For more informations on these models you …

Plotting regression curves with confidence intervals for LM, GLM and GLMM in R

[Updated 22nd January 2017, corrected mistakes for getting the fixed effect estimates of factor variables that need to be averaged out] [Updated 14th July 2017, the function is now on github: https://github.com/Lionel68/Blog/tree/master/PlotFit any modifications to it will be posted there before updating the post. The function has 2 new functionalities: (i) taking into account offset …

Two little annoying stats detail

UPDATED: Thanks to Ben and Florian comments I've updated the first part of the post   A very brief post at the end of the field season on two little “details” that are annoying me in paper/analysis that I see being done (sometimes) around me. The first one concern mixed effect models where the models …