To cite package ‘rspatial’ in publications use:

  Hijmans R (2018). _rspatial: rspatial.org data_. R package version
  1.0-0, <https://github.com/rspatial/rspatial>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {rspatial: rspatial.org data},
    author = {Robert J. Hijmans},
    year = {2018},
    note = {R package version 1.0-0},
    url = {https://github.com/rspatial/rspatial},
  }