Nonlinear Mixed Effects Models in Population PK/PD, Extra Support Functions R package nlmixr2extra version 5.1.0 Fit and compare nonlinear mixed-effects models in differential equations with flexible dosing information commonly seen in pharmacokinetics and pharmacodynamics (Almquist, Leander, and Jirstrand 2015 <doi:10.1007/s10928-015-9409-1>). Differential equation solving is by compiled C code provided in the 'rxode2' package (Wang, Hallow, and James 2015 <doi:10.1002/psp4.12052>). This package is for support functions like preconditioned fits <doi:10.1208/s12248-016-9866-5>, boostrap and stepwise covariate selection. Software Depends: R (>= 4.1) Imports: checkmate, cli (>= 3.4.0), crayon, data.table, digest, dplyr, ggplot2, ggtext, knitr, lotri, magrittr, methods, nlme, nlmixr2est (>= 6.0.0), Rcpp, rxode2 (>= 5.1.0), stats, symengine, utils LinkingTo: Rcpp, RcppArmadillo Suggests: brms, nlmixr2data, rmarkdown, tidyr, nlmixr2lib, testthat (>= 3.0.0), withr Matthew Fidler <matthew.fidler@gmail.com> Comprehensive R Archive Network (CRAN) Matthew Fidler [aut, cre] (ORCID: <https://orcid.org/0000-0001-8538-6691>), Vipul Mann [aut], Vishal Sarsani [aut] (ORCID: <https://orcid.org/0000-0002-9272-3438>), Christian Bartels [ctb], Bill Denney [aut] (ORCID: <https://orcid.org/0000-0002-5759-428X>), Omar Elashkar [ctb] (ORCID: <https://orcid.org/0000-0002-5505-778X>) GPL (>= 3) 2026-06-07 application/tgz https://CRAN.R-project.org/package=nlmixr2extra doi:10.32614/CRAN.package.nlmixr2extra