To cite package ‘grumpy’ in publications use:

  Gruson H, Smith M (2026). _grumpy: Read 'NumPy' '.npy' and '.npz'
  Files_. R package version 0.1.1,
  <https://CRAN.R-project.org/package=grumpy>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {grumpy: Read 'NumPy' '.npy' and '.npz' Files},
    author = {Hugo Gruson and Mike Smith},
    year = {2026},
    note = {R package version 0.1.1},
    url = {https://CRAN.R-project.org/package=grumpy},
  }