Color admin groups so touching neighbors never share a color — plot_admin_map

This function takes an adm2-level shapefile, dissolves it into a higher administrative level (e.g., provinces at adm1), constructs a neighbor graph, assigns colors to the aggregated units ensuring that no adjacent units share the same color, and then maps those colors back to the adm2 polygons. Labels are placed at the centroid of each higher-level unit, and a ggplot2 map is produced. The plot can optionally be saved as a PNG.

Usage

plot_admin_map_distinct(
  shp,
  group_col,
  id_col,
  out_png = NULL,
  palette = c("#D95F02", "#1B9E77", "#7570B3", "#E7298A", "#66A61E", "#E6AB02"),
  fix_valid = FALSE
)

Arguments

shp: sf. Polygon layer at adm2 level containing a column for the higher-level grouping (adm1) and unique adm2 identifiers.
group_col: character. Column name for higher-level admin grouping (e.g., adm1).
id_col: character. Column name for unique adm2 identifiers.
out_png: character|NULL. File path to save PNG output. If NULL, no file is saved.
palette: character. Vector of hex colors to use for coloring groups. Will be recycled if there are more groups than colors.
fix_valid: logical. If TRUE, run sf::st_make_valid() to fix invalid geometries before processing.

Value

A list with three components:

shp: sf with group colors joined back to adm2 polygons
labels: sf with label coordinates (x, y) for each group
gg: ggplot object of the colored map with labels

Examples

# Not run:
# res <- plot_admin_map_distinct(
#   shp = shp_output_old$spat_vec$adm2,
#   group_col = "adm1",
#   id_col = "adm2",
#   out_png = here::here("03_outputs/plots/burundi_health_dist_old2.png")
# )
# print(res$gg)