To cite package ‘lookup’ in publications use:

  Wright K (2024). _lookup: Functions Similar to VLOOKUP in Excel_. R
  package version 1.0, <https://github.com/kwstat/lookup>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {lookup: Functions Similar to VLOOKUP in Excel},
    author = {Kevin Wright},
    year = {2024},
    note = {R package version 1.0},
    url = {https://github.com/kwstat/lookup},
  }