graphique alluvial

Code R de l'exemple ggplot2

library(ggplot2)
library(dplyr)
library(tidyr)
library(ggalluvial)
library(gapminder)

## Countries by life-expectancy band in 1952, 1977 and 2007. As in Brunson
## (2020), each ribbon (geom_alluvium) follows the same countries from one
## date to the next and keeps the color of their continent: one ribbon per
## continent and path.
## Data modified for the example: 20 countries, drawn at random among those
## not named in the title, are removed in 1952 and enter in 1977, so that the
## columns differ in height.
late <- c("Austria", "Chad", "Djibouti", "Equatorial Guinea", "Ethiopia", "Ghana",
          "Greece", "Haiti", "Israel", "Myanmar", "Pakistan", "Peru", "Poland",
          "Romania", "Sao Tome and Principe", "Sudan", "Sweden", "Switzerland",
          "United Kingdom", "Uruguay")
paths <- gapminder |>
  filter(year %in% c(1952, 1977, 2007)) |>
  mutate(band = cut(lifeExp, c(0, 50, 65, Inf), right = FALSE,
                    labels = c("Under 50", "50 to 65", "Over 65")),
         band = if_else(year == 1952 & country %in% late, NA, band)) |>
  select(country, continent, year, band) |>
  pivot_wider(names_from = year, values_from = band) |>
  count(continent, `1952`, `1977`, `2007`) |>
  mutate(path = row_number())

## One row per path and date (lodes form); a path that starts in 1977 has
## no 1952 row, so its ribbon starts there.
lodes <- paths |>
  pivot_longer(c(`1952`, `1977`, `2007`), names_to = "year", values_to = "band") |>
  filter(!is.na(band))

p <- ggplot(lodes, aes(x = year, stratum = band, alluvium = path, y = n)) +
  geom_alluvium(aes(fill = continent), width = 0.3, colour = "white", linewidth = 0.2,
                alpha = 0.9) +
  geom_stratum(width = 0.3, fill = "#535353", colour = "white", linewidth = 0.3) +
  geom_text(stat = "stratum", aes(label = after_stat(stratum)), colour = "white", size = 2.8) +
  scale_fill_manual(values = continent_colors) +
  scale_x_discrete(expand = expansion(add = 0.2)) +
  labs(title = "Twelve African countries and Afghanistan stayed\nunder 50 years of life expectancy from 1952 to 2007",
       subtitle = "Life expectancy at birth, 122 countries in 1952 and 142 from 1977;\neach ribbon follows the same countries to 2007",
       x = NULL, y = "Countries", fill = NULL,
       caption = "Data: gapminder (Bryan 2025), modified: 20 countries removed in 1952") +
  theme_lex_viz(grid = "", arrows = "") +
  theme(legend.position = "bottom", axis.text.x = element_text(face = "bold"))