dasymetric map

Code R de l'exemple ggplot2

library(ggplot2)
library(dplyr)
library(sf)
library(patchwork)

## Communes of the Hautes-Alpes, their land cover (Corine Land Cover 2018) and
## their built or farmed land, prepared by tools/donnees_dasymetrique.R.
gpkg <- "illustrations/ggplot/data/dasymetric-map.gpkg"
communes <- st_read(gpkg, "communes", quiet = TRUE)
land <- st_read(gpkg, "occupation", quiet = TRUE)
habitable <- st_read(gpkg, "habitable", quiet = TRUE) |>
  left_join(st_drop_geometry(communes), by = "code") |>
  mutate(density = population / (as.numeric(st_area(geom)) / 1e6))

## One dot for 50 people, drawn anywhere in its commune: all that is known
## before the land cover is brought in.
set.seed(1)
dots <- st_sample(communes, size = round(communes$population / 50))

borders <- geom_sf(data = communes, fill = NA, colour = "grey70", linewidth = 0.1)
## The theme goes to each map, not to the whole: the "+" and "=" stay bare.
map <- function(p, legend = "none") {
  p + coord_sf(datum = NA) +
    theme_lex_viz(base_size = 7, grid = "", arrows = "") +
    theme(legend.position = legend, legend.key.size = unit(2.5, "mm"))
}
p1 <- map(ggplot() + borders + geom_sf(data = dots, size = 0.15, shape = 16, stroke = 0) +
  labs(subtitle = "People (1 dot = 50)"))
## Four of the Rattner colors, each given to the land cover it evokes.
p2 <- map(ggplot() +
  geom_sf(data = land, aes(fill = groupe), colour = NA) +
  scale_fill_manual(values = c(built = "#de8e69", farmland = "#a39fc9",
                               `forest and natural` = "#7a9132",
                               `water and wetlands` = "#4c849a")) +
  guides(fill = guide_legend(ncol = 2)) +
  labs(subtitle = "Land cover", fill = NULL), "bottom")
p3 <- map(ggplot() + borders +
  geom_sf(data = habitable, aes(fill = density), colour = NA) +
  scale_fill_continuous(transform = "log10", breaks = c(10, 100, 1000),
                        labels = lex_number) +
  guides(fill = guide_colourbar(barwidth = unit(25, "mm"))) +
  labs(subtitle = "People per km² of built or farmed land", fill = NULL), "bottom")
sign <- function(s) {
  ggplot() + annotate("text", x = 0, y = 0, label = s, size = 6) + theme_void()
}

p <- p1 + sign("+") + p2 + sign("=") + p3 +
  plot_layout(nrow = 1, widths = c(1, 0.12, 1, 0.12, 1)) +
  plot_annotation(
    title = "Hautes-Alpes: population spread over built and farmed land",
    subtitle = "16% of the area is left once forests, high mountains and water are removed: 153 people per km² there, compared with 25 across the whole department",
    caption = "Data: INSEE and IGN via geo.api.gouv.fr (Licence Ouverte);\nCorine Land Cover 2018, © European Union, Copernicus Land Monitoring Service",
    theme = theme_lex_viz(base_size = 7, grid = "", arrows = "")
  )