R package - HultenRangeMaps

This dataset contains an R package (R Core Team 2025) with the methods employed to digitise the historical range maps in the ‘Atlas of the distribution of vascular plants in northwestern Europe’ (Hultén 1971). Methods include georeferencing the scanned maps, extract range data, clean data and convert data from raster to spatial polygon data. A detailed description of how the original atlas was compiled as well as the method used to georeference and digitize the distribution maps can be found in Arnell et al. (2026a). The resulting dataset can be found at https://doi.org/10.58141/y1x5-cx68 (Arnell et al. 2026b).

A package tutorial with examples can be found at GitHub https://github.com/ArnellM/HultenRangeMaps/.

The package contains two functions to extract and clean distribution data from the scanned maps, one function to modify file names and one function to match the distribution data to polygon grids commonly used when analysing historical atlas data.

Installation
This package can be installed using devtools (Wickham et al. 2025). To insure reproducibility, we have created a ‘mini’ repository with all the packages that the functions in HultenRangeMaps require. The repository is included in the documentation files (HultenRangeMaps_miniCRAN_June2025.zip) and at GitHub https://github.com/ArnellM/HultenRangeMaps_miniCRAN_June2025. First, download the repository to your computer. Then, decompress the folder and install the packages from your local repository using the code below.

# list of packages that the functions in HultenRangeMaps require
pkgs <- c("dplyr", "gtools", "raster", "sf", "terra", "tidyr")

# path to where you have downloaded the local miniCran repository
pth <- "/HultenRangeMaps_miniCRAN_June2025"

# install packages from your local miniCRAN repository
install.packages(pkgs, repos = paste0("file:///", pth), type = "source")

# install HultenRange maps
install.packages(c("devtools", "rtools"))
library(devtools)
install_github("ArnellM/HultenRangeMaps")
library(HultenRangeMaps)

References
Arnell, M., Auffret, A. G., & Hylander, K. (2026a). Historical distribution maps of vascular plants in Northern Europe. (Accepted for publication in Ecology).

Arnell, M., Auffret, A. G., & Hylander, K. (2026b). Historical distribution maps of vascular plants in Northern Europe (Version 1) [Data set]. Stockholm University. https://doi.org/10.58141/y1x5-cx68

Hultén E. (1971). Atlas of the distribution of vascular plants in northwestern Europe (2nd ed.). Generalstabens Litografiska Anstalts Förlag.

R Core Team. (2025). R: A language and environment for statistical computing [Computer software]. R Foundation for Statistical Computing. https://www.R-project.org/

Wickham H., Hester J., Chang W., Bryan J. (2025). devtools: Tools to Make Developing R Packages Easier. R package version 2.4.6, https://devtools.r-lib.org/.