To cite package ‘cinterpolate’ in publications use:

  FitzJohn R (2024). _cinterpolate: Interpolation From C_. R package
  version 1.0.2, <https://github.com/mrc-ide/cinterpolate>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {cinterpolate: Interpolation From C},
    author = {Rich FitzJohn},
    year = {2024},
    note = {R package version 1.0.2},
    url = {https://github.com/mrc-ide/cinterpolate},
  }