carto_facet.R

# World basemap
download.file(url = "https://raw.githubusercontent.com/riatelab/basemaps/master/World/countries.geojson",
              destfile = "country.geojson")
# Graticules layer
download.file(url = "https://raw.githubusercontent.com/riatelab/basemaps/master/World/graticule30.geojson",
              destfile = "graticule.geojson")
# Population data base
download.file(url = "https://population.un.org/wup/Download/Files/WUP2018-F12-Cities_Over_300K.xls",
              destfile = "citypop.xls")

# libraries
library(sf)
library(cartography)
library(readxl)

# import
country <- st_read(dsn = "country.geojson", quiet = TRUE)
graticule <- st_read(dsn = "graticule.geojson", quiet = TRUE)
city <- data.frame(read_excel("citypop.xls", skip = 16))
# construction de la couche city
city <- st_as_sf(city,
                 coords = c("Longitude", "Latitude"),
                 crs = 4326)
# transformation de la projection WGS84 => Robinson
country <- st_transform(x = country, crs = 54030)
graticule <- st_transform(x = graticule, crs = 54030)
city <- st_transform(x = city, crs = 54030)
# selection des 50 plus grandes villes de 2035
cityx <- city[order(city$X2035, decreasing = T),][1:50, ]


# l'argument mfrow de la fonction par() permet de définir le découpage de la
# fenêtre graphique. Ici 6 lignes sur 3 colonnes.
par(mfrow = c(6, 3), mar = c(0.1, 0.1, 0.1, 0.1))

# Dans cette boucle nous parcourons les noms des colonnes à représenter:
# names(cityx)[7:24]
for (i in names(cityx)[7:24]) {
  # affichage des graticules
  plot(
    st_geometry(graticule),
    col = "lightblue",
    border = "white",
    lwd = 0.2,
    bg = "cornsilk2"
  )
  # affichage des pays
  plot(
    st_geometry(country),
    col = "ivory4",
    border = "ivory3",
    lwd = 0.5,
    add = TRUE
  )
  # affichages des symboles proportionnels
  propSymbolsLayer(
    x = cityx,
    var = i,
    col = "darkred",
    legend.pos = "n",
    fixmax = 43000,
    border = "white",
    lwd = 0.5,
    inches = 0.1
  )
  # affichage des légendes "custom"
  legendCirclesSymbols(
    pos = "bottomleft",
    title.txt = "Pop (milliers)",
    title.cex = 0.8,
    cex = 0.7,
    col = "darkred",
    var = c(1000, 7000, 20000, 43000),
    inches = 0.1
  )
  # affichage de l'année
  text(
    x = -14900000,
    y = 8000000,
    labels = substr(i, 2, 5),
    cex = 1.5,
    font = 2
  )
}