The VetResearchLMM package provides the datasets and reproducible R examples that accompany Duchateau, Janssen, and Rowlands (1998), Linear Mixed Models: An Introduction with Applications in Veterinary Research. The package is intended for readers who want to reproduce, inspect, and adapt the linear mixed model examples from the book using current R tooling.
School of Mathematical and Statistical Sciences, Clemson University, Clemson, South Carolina, USA.
The Quarto vignettes provide an introduction, methodology overview, chapter/example walkthrough, and plotting guide:
vetresearchlmm-introduction
vetresearchlmm-methodology
vetresearchlmm-examples
vetresearchlmm-plotting
Muhammad Yaseen myaseen208@gmail.com
The package focuses on small applied veterinary research examples involving
fixed effects, random effects, variance components, nested designs,
repeated measurements, and basic hypothesis tests for linear mixed models.
The package also includes report_mixed_model() and
emmeans_mixed_model(), small helpers that delegate fitted model
interpretation and post hoc marginal-mean inference to the optional
report and emmeans packages when they are installed. The main
user-facing data objects are the book datasets:
ex121Dose comparison data for packed cell volume.
ex124Herd, drug, and dose packed cell volume data.
ex125Region, drug, and dose split-plot data.
ex127Sire-level weaning weight data.
ex31Designed experiment data for PCV response.
ex32Breed, sire, sex, age, and weaning weight data.
ex33Longitudinal PCV data by animal and breed.
The example help pages reproduce the corresponding analyses with modern R packages such as lme4, lmerTest, nlme, multcomp, collapse, ggplot2, and emmeans where those packages are available. Numerical results can differ slightly from the book because the book reports SAS output and modern R packages use their own optimizers, parameterizations, and degrees-of-freedom methods.
A typical workflow is:
Load one of the included datasets with data().
Inspect the matching example help page, such as
?Examp2.4.2.2.
Fit the fixed effect or mixed model shown in the example.
Compare estimates, variance components, and tests with the book.
Use report_mixed_model() for an optional narrative
model report when report is installed.
Use emmeans_mixed_model() for optional estimated
marginal means and post hoc comparisons when emmeans is installed.
Use the package vignettes for chapter-level narrative examples.
Duchateau, L., Janssen, P., and Rowlands, G. J. (1998). Linear Mixed Models: An Introduction with Applications in Veterinary Research. International Livestock Research Institute.