To cite package ‘comorbidity’ in publications use:

  Gasparini, (2018). comorbidity: An R package for computing
  comorbidity scores. Journal of Open Source Software, 3(23), 648,
  https://doi.org/10.21105/joss.00648

A BibTeX entry for LaTeX users is

  @Article{,
    author = {Alessandro Gasparini},
    title = {comorbidity: An R package for computing comorbidity scores},
    journal = {Journal of Open Source Software},
    year = {2018},
    volume = {3},
    issue = {23},
    pages = {648},
    doi = {10.21105/joss.00648},
    url = {https://doi.org/10.21105/joss.00648},
  }