Inaccessibility
R-bloggers 2025-11-07
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Day 7 of 30DayMapChallenge: « Accessibility » (previously).
Well, let us be rebellious and instead seek inaccessibility; more precisely the pole of inaccessibility of France (the Hexagon): the farthest location from the boundary. Not to be confused with the centroid.
library(sf)library(dplyr)library(ggplot2)library(glue)library(purrr)library(polylabelr)
Data
We’ll use again the french administrative units (get the data from this post).
# France boundaryfr <- read_sf("~/data/adminexpress/adminexpress_cog_simpl_000_2022.gpkg", layer = "region") |> filter(insee_reg > "06", insee_reg != "94") |> st_transform("EPSG:2154") |> st_union()# French communes to get the point namecom <- read_sf("~/data/adminexpress/adminexpress_cog_simpl_000_2022.gpkg", layer = "commune") |> filter(insee_reg > "06", insee_reg != "94") |> st_transform("EPSG:2154")Compute the POI
Get the inaccessibility pole of France with {polylabelr} and intersects with the commune layer to find the nearest city.
fr_poi <- poi(fr) |> pluck(1) |> as_tibble() |> st_as_sf(coords = c("x", "y"), crs = "EPSG:2154") |> st_join(com)fr_poi_circle <- fr_poi |> mutate(geometry = st_buffer(geometry, dist))fr_centroid <- fr |> st_centroid()It seems to be in Saint-Palais in the Cher département.
Map
fr_poi |> ggplot() + geom_sf(data = fr) + geom_sf(data = fr_poi_circle, linewidth = 1, linetype = 3) + geom_sf(data = fr_centroid, color = "darkgrey") + geom_sf() + geom_sf_text(aes(label = nom), vjust = -.5) + labs(title = "Pole of inaccessibility", subtitle = "France", x = "", y = "", caption = glue("https://r.iresmi.net/ - {Sys.Date()} data from IGN Adminexpress 2022")) + theme_minimal() + theme(plot.caption = element_text(size = 6, color = "darkgrey"))
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