Please cite the jpmapdata package whenever you use its boundary data.

Horiuchi Y (2026). jpmapdata: Boundary Data for Japan Maps. Comprehensive R Archive Network (CRAN). doi:10.32614/CRAN.package.jpmapdata. R package version 0.1.0, https://CRAN.R-project.org/package=jpmapdata.

Corresponding BibTeX entry:

  @Manual{jpmapdata,
    title = {jpmapdata: Boundary Data for Japan Maps},
    author = {Yusaku Horiuchi},
    year = {2026},
    note = {R package version 0.1.0},
    organization = {Comprehensive R Archive Network (CRAN)},
    doi = {10.32614/CRAN.package.jpmapdata},
    url = {https://CRAN.R-project.org/package=jpmapdata},
  }