unit chart

R code of the ggplot2 example

library(ggplot2)
library(dplyr)
library(palmerpenguins)

## One dot per penguin, stacked by island in rows of ten.
units <- penguins |>
  arrange(island, species) |>
  group_by(island) |>
  mutate(position = row_number() - 1,
         x = position %% 10,
         y = position %/% 10) |>
  ungroup()
## Each species named once, in its colour, above an island where it was sampled.
names_at <- tibble(species = c("Gentoo", "Chinstrap", "Adelie"),
                   island = c("Biscoe", "Dream", "Torgersen")) |>
  left_join(units |> group_by(island) |> summarise(top = max(y)), by = "island") |>
  mutate(x = 4.5, y = top + 2)

p <- ggplot(units, aes(x = x, y = y, colour = species)) +
  geom_point(size = 1.3) +
  geom_text(data = names_at, aes(label = species), size = 3.2) +
  facet_wrap(~island, nrow = 1, strip.position = "bottom") +
  scale_y_continuous(expand = expansion(mult = c(0.02, 0.04))) +
  coord_fixed() +
  labs(title = "Only Adelies were sampled on all three islands",
       subtitle = "344 penguins of the Palmer Archipelago, one dot each",
       x = NULL, y = NULL,
       caption = "Data: palmerpenguins (Horst, Hill & Gorman 2020)") +
  theme_lex_viz(grid = "", arrows = "") +
  theme(legend.position = "none", axis.text = element_blank())