hexgridmap

Overview

hexgrid transforms irregular spatial polygons into a hexagonal grid representation, making it easier to visualize geographical patterns when dealing with polygons of vastly different sizes. This is particularly useful when working with administrative boundaries like parishes, municipalities, or census tracts that vary dramatically in size.

For example, when visualizing Swedish parishes, the tiny Stockholm domkyrka and vast Jukkasjärvi parish can be represented more effectively using standardized hexagonal units while maintaining their spatial relationships.

Features

• Converts irregular polygons to a standardized hexagonal grid
• Combines small polygons into single hexagons
• Allows large polygons to span multiple hexagons
• Preserves spatial relationships
• Handles edge cases and partial coverage
• Maintains linkage between original polygons and hex units

Installation

You can install the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("junkka/hexgridmap")

Usage

Here's a basic example:

library(hexgridmap)
library(sf)
library(ggplot2)

# Read your spatial data
parishes <- read_sf("path/to/parishes.shp")

# Create hexagonal representation
result <- create_hex_map(
  sf_object = parishes,
  hex_size = 25000,  # 25km in projection units
  min_coverage = 0.2,
  id_col = "parish_id",
  name_col = "name"
)

# Plot the result
ggplot(result$hex_sp) +
  geom_sf(aes(fill = geom_ids)) +
  theme_minimal() +
  ggtitle("Parish Hexagonal Representation")

# Check assignments
head(result$hex_links)

Use Cases

The package is particularly useful for:

• Visualizing administrative boundaries of varying sizes
• Creating standardized choropleth maps
• Comparing spatial patterns across regions with different polygon sizes
• Generating tile-based representations of irregular spatial data

Function Documentation

create_hex_map()

Main function for creating hexagonal grid representations.

Arguments:

• sf_object: An sf object containing the polygons to be transformed
• hex_size: Size of hexagonal cells in the same units as sf_object
• min_coverage: Minimum proportion (0-1) of hex that must be covered
• id_col: Name of column containing unique identifiers
• name_col: Optional column name containing polygon names

Returns: A list with two elements:

• hex_sp: An sf object containing the hexagonal grid
• hex_links: A data frame linking original polygon IDs to hex assignments

Citation

If you use this package in your research, please cite it as:

@misc{hexgridmap2024,
  author = {Johan Junkka},
  title = {hexgridmap: Transform Irregular Spatial Polygons into Hexagonal Grid Representation},
  year = {2024},
  publisher = {GitHub},
  url = {https://github.com/junkka/hexgridmap}
}

Related Work

• sf: Simple Features for R
• histmaps: Historical Maps of Sweden