From nlmixr2 Working Group: nlmixr2 inter occasion variability

nlmixr2, a R-based open-source nonlinear mixed-effects modeling software package that can compete with commercial pharmacometric tools and is suitable for regulatory submissions, now supports inter-occasion variability!
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Author

R Consortium

Published

February 3, 2026

Original post on the nlmixr2 project blog is here.

From the nlmixr2 project blog:

Inter-occasion variability Happy new year! With the holidays over we had the opportunity to celebrate many special occasions.

I invite you to celebrate a new occasion for nlmixr2 – inter-occasion variability.

We now support inter-occasion variability estimation in nlmixr2!

Implementing inter-occasion variability in models

To implement inter-occasion variability in nlmixr2 models you simply have to specify that the variable is an occasion variable, say occ:

iov.cl ~ 0.1 | occ

Full article on the nlmixr2 project blog is here.

Previous announcement from November 2025: nlmixr2 is Becoming an R Consortium Working Group

Get involved in the nlmixr2 working group

The nlmixr2 working group is open to anyone interested in contributing to the project. You can get involved by:

Main repo: https://github.com/nlmixr2/nlmixr2
Issues: https://github.com/nlmixr2/nlmixr2/issues
Discussions: https://github.com/nlmixr2/nlmixr2/discussions