Plot Municipal Choropleth Maps

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This example uses official MLIT N03 municipal boundaries for Okinawa Prefecture as of January 1, 2024. It maps one simple fill variable: 2020 census population by municipality. The figure focuses on Okinawa Island so the municipal boundaries are legible; the source boundary file can still contain the rest of Okinawa Prefecture.

Population values are 2020 Census values from Statistics Bureau Japan as tabulated by CityPopulation.de.

library(tidyverse)
library(jpmap)

okinawa_main_island <- c(
  "那覇市", "宜野湾市", "浦添市", "名護市", "糸満市", "沖縄市",
  "豊見城市", "うるま市", "南城市", "国頭村", "大宜味村", "東村",
  "今帰仁村", "本部町", "恩納村", "宜野座村", "金武町", "読谷村",
  "嘉手納町", "北谷町", "北中城村", "中城村", "西原町", "与那原町",
  "南風原町", "八重瀬町"
)

okinawa_population_2020 <- tribble(
  ~municipality_ja, ~population_2020,
  "那覇市", 317625L,
  "宜野湾市", 100125L,
  "浦添市", 115690L,
  "名護市", 63554L,
  "糸満市", 61007L,
  "沖縄市", 142752L,
  "豊見城市", 64612L,
  "うるま市", 125303L,
  "南城市", 44043L,
  "国頭村", 4517L,
  "大宜味村", 3092L,
  "東村", 1598L,
  "今帰仁村", 8894L,
  "本部町", 12530L,
  "恩納村", 10869L,
  "宜野座村", 5833L,
  "金武町", 10806L,
  "読谷村", 41240L,
  "嘉手納町", 13521L,
  "北谷町", 28201L,
  "北中城村", 17969L,
  "中城村", 22157L,
  "西原町", 34984L,
  "与那原町", 19695L,
  "南風原町", 40440L,
  "八重瀬町", 30941L
)

okinawa_main_island_min_area <- 5e6
keep_okinawa_main_island <- function(map) {
  filtered <- map |>
    filter(municipality_ja %in% okinawa_main_island)

  filtered |>
    mutate(area_m2 = as.numeric(sf::st_area(filtered))) |>
    filter(area_m2 >= okinawa_main_island_min_area) |>
    select(-area_m2)
}

okinawa_main_map <- jp_map("municipality", include = "Okinawa", inset = FALSE) |>
  keep_okinawa_main_island() |>
  jp_map_join(okinawa_population_2020, by = "municipality_ja")

ggplot(okinawa_main_map) +
  geom_sf(
    aes(fill = population_2020),
    color = "grey35",
    linewidth = 0.12
  ) +
  coord_sf(
    crs = jpmap_crs(),
    datum = sf::st_crs(4326)
  ) +
  scale_fill_gradient(
    low = "#EAF2FF",
    high = "#001040",
    labels = function(x) format(x, big.mark = ",", scientific = FALSE),
    name = "Population"
  ) +
  labs(
    title = "Okinawa Island municipality population",
    caption = paste(
      "Boundary: MLIT N03, January 1, 2024.",
      "Population: 2020 Census, Statistics Bureau Japan via CityPopulation.de.",
      sep = "\n"
    )
  ) +
  theme_gray() +
  theme(
    axis.title = element_blank(),
    panel.grid.minor = element_blank(),
    legend.background = element_rect(fill = "white", color = NA),
    plot.title = element_text(face = "bold", color = "#001040"),
    plot.caption = element_text(color = "#2C2A29", hjust = 0, size = 8)
  )

For other prefectures, first build the prefecture’s municipal boundaries with jpmap_build_data(year = 2024, prefecture = "..."), then join a table with one row per municipality.

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.