To cite brokenstick in publications use:

van Buuren S (2022). “Broken Stick Model for Irregular Longitudinal Data.” Journal of Statistical Software, Submitted for publication(X), X-X. https://github.com/growthcharts/brokenstick.

Corresponding BibTeX entry:

  @Article{,
    title = {Broken Stick Model for Irregular Longitudinal Data},
    author = {Stef {van Buuren}},
    journal = {Journal of Statistical Software},
    year = {2022},
    volume = {Submitted for publication},
    number = {X},
    pages = {X-X},
    url = {https://github.com/growthcharts/brokenstick},
  }