diagramme en arc

Code R de l'exemple ggplot2

library(ggplot2)
library(dplyr)
library(igraph)
library(ggraph)

## Friendships named in 1958, marked by whether the same boy named the same
## friend in 1957. Boys ordered by the groups the Louvain method finds.
boys <- sort(unique(c(highschool$from, highschool$to)))
in_1957 <- with(filter(highschool, year == 1957), paste(from, to))
ties <- highschool |>
  filter(year == 1958) |>
  mutate(since = ifelse(paste(from, to) %in% in_1957, "Already in 1957", "New in 1958")) |>
  select(from, to, since)
named <- graph_from_data_frame(ties, vertices = data.frame(name = boys))
set.seed(1)
V(named)$group <- as.integer(membership(cluster_louvain(as_undirected(named, mode = "collapse"))))

p <- ggraph(named, layout = "linear", sort.by = group) +
  geom_edge_arc(aes(edge_colour = since, edge_linetype = since), fold = TRUE, edge_width = 0.3,
                edge_alpha = 0.6) +
  geom_node_point(size = 0.8, colour = "#535353") +
  ## The line type tells the two kinds apart without the colours.
  annotate("segment", x = 1, xend = 5, y = c(20, 17), yend = c(20, 17),
           colour = c("#9b2367", "#2e7891"), linetype = c("dotdash", "solid"), linewidth = 0.5) +
  annotate("text", x = 6, y = 20, label = "Already in 1957", colour = "#9b2367", hjust = 0, size = 3.2) +
  annotate("text", x = 6, y = 17, label = "New in 1958", colour = "#2e7891", hjust = 0, size = 3.2) +
  scale_edge_colour_manual(values = c(`Already in 1957` = "#9b2367", `New in 1958` = "#2e7891")) +
  scale_edge_linetype_manual(values = c(`Already in 1957` = "dotdash", `New in 1958` = "solid")) +
  labs(title = "Just over half of the 1958 friendships\nwere already named in 1957",
       subtitle = "Who names whom in a high school, boys ordered by Louvain group",
       caption = "Data: Coleman 1964, via the ggraph R package") +
  theme_lex_viz(grid = "", arrows = "") +
  theme(legend.position = "none", axis.text = element_blank(), axis.title = element_blank())