Place Striptext inside Facet Panels with ggplot2

striptext-inside.R

library(ggplot2)

gm_2023 <- readr::read_csv("https://www.cedricscherer.com/data/gapminder-2023.csv")
pal <- c(Africa = "#00D9EE", Americas = "#4CF101", Asia = "#FF4670", Europe = "#FFE702", Oceania = "#CA4ADC")

# base plot
g <-
  ggplot(gm_2023, aes(x = gdp_pcap, y = life_exp, size = pop)) +
  geom_point(
    color = "white", 
    layout = "fixed"
  ) +
  geom_point(
    shape = 21, fill = "grey65", color = "white", alpha = .3, 
    layout = "fixed"
  ) +
  geom_point(
    shape = 21, aes(fill = continent), alpha = .7, stroke = .7
   ) +
  scale_x_log10(
    labels = scales::label_dollar(),
    name = "GDP per capita (int$, log scale)",
    breaks = 1000 * 2^(-1:7)
  ) +
  scale_y_continuous(
    breaks = seq(30, 90, by = 5), name = "Life expectancy in years",
    expand = expansion(add = c(2, 3))
  ) +
  scale_fill_manual(
    values = pal, guide = "none"
  ) +
  scale_size(
    range = c(.8, 20),
    breaks = 1 * 10^(6:9),
    labels = c("1M", "10M", "100M", "1 billion\nhumans"),
    name = "Area by Population:",
    guide = guide_legend(override.aes = list(fill = "#9FBBC1"))
  ) +
  facet_wrap(~continent, nrow = 5) +
  theme_bw(base_family = "Atkinson Hyperlegible") +
  theme(
    panel.grid.minor = element_blank(),
    panel.spacing = unit(1, "lines"),
    plot.margin = margin_auto(12),
    legend.justification = "top",
    legend.box.margin = margin_part(t = 40),
    axis.title.x = element_text(hjust = 0, margin = margin_part(t = 12)),
    axis.title.y = element_text(hjust = .98, margin = margin_part(r = 12)),
    strip.background = element_blank(),
    strip.text = element_text(face = "bold", hjust = 0, size = rel(1.4))
  )

g


# labels disappear if strip.clip is "on" (default behavior)
g + theme(strip.text = element_text(margin = margin_part(b = -20, l = 8)))

# turn off striptext clipping (and adjust spacings)
g +
  theme(
    strip.text = element_text(margin = margin_part(b = -20, l = 8)),
    strip.clip = "off",
    panel.spacing = unit(2, "lines"),
    plot.margin = margin(t = 24, r = 12, b = 12, l = 12)
  )

# version with geom_label() instead
g +
  geom_label(
    aes(label = continent, x = 350, y = 81),
    stat = "unique", size = 5, hjust = 0,
    family = "Atkinson Hyperlegible", fontface = "bold"
  ) +
  theme(
    strip.text = element_blank()
  )

# version with colored labels
g +
  geom_text(
    aes(label = continent, x = 350, y = 82.5, 
        # hacky trick to avoid specfying color scale
        fill = continent, color = after_scale(colorspace::darken(fill, .35))),
    stat = "unique", size = 5, hjust = 0,
    family = "Atkinson Hyperlegible", fontface = "bold"
  ) +
  theme(
    strip.text = element_blank()
  )