diagramme 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 Rosvall &
## Bergstrom (2010), flows only join adjacent dates (geom_flow): each flow
## takes the color of the band it leaves, and a band receives as much as it
## sends.
bands <- 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"))) |>
  select(country, year, band)

p <- ggplot(bands, aes(x = factor(year), stratum = band, alluvium = country)) +
  geom_flow(aes(fill = band), aes.flow = "forward", 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 = unname(lex_colors)) +
  scale_x_discrete(expand = expansion(add = 0.2)) +
  labs(title = "Six countries fell back below 50 years of life expectancy\nbetween 1977 and 2007",
       subtitle = "142 countries by life expectancy at birth; each flow takes the color\nof the band it leaves",
       x = NULL, y = "Countries",
       caption = "Data: gapminder (Bryan 2025)") +
  theme_lex_viz(grid = "", arrows = "") +
  theme(legend.position = "none", axis.text.x = element_text(face = "bold"))