troubleshooting {lme4}R Documentation



This page attempts to summarize some of the common problems with fitting [gn]lmer models and how to troubleshoot them.

Most of the symptoms/diagnoses/workarounds listed below are due to various issues in the actual mixed model fitting process. You may run into problems due to multicollinearity or variables that are incorrectly typed (e.g. a variable is accidentally coded as character or factor rather than numeric). These problems can often be isolated by trying a lm or glm fit or attempting to construct the design matrix via model.matrix() (in each case with the random effects in your model excluded). If these tests fail then the problem is likely not specifically an lme4 issue.

[Package lme4 version 1.1-32 Index]