https://cran.r-universe.dev/Directionalhttps://cran.r-universe.dev/api/packages/Directionalhttps://cran.r-universe.dev/Directional/Directional.pdfhttps://cran.r-universe.dev/Directional/doc/manual.htmlhttps://cran.r-universe.dev/Directional/citationhttps://cran.r-universe.dev/Directional/citation.txthttps://cran.r-universe.dev/Directional/citation.cff