ggplot add country names in legend below geom_map

Question

I would like to add a legend for the country names below my map.

I have this dataframe of frequency of event occurrences on different regions:

trend_country_freq  <- structure(list(country = c("US", "CN", "KR", "IN", "AU", "GB", 
"JP"), n = c(25L, 20L, 12L, 5L, 2L, 1L, 1L), country_name = c("USA", 
"China", "South Korea", "India", "Australia", "UK", "Japan")), row.names = c(1L, 
2L, 3L, 4L, 5L, 7L, 8L), class = "data.frame")

Now I use the maps and ggplot2 packages to create a world map showing the frequency of event occurences:

library(maps)
library(ggplot2)

world_map <- map_data("world")
world_map <- subset(world_map, region != "Antarctica")

ggplot(trend_country_freq) +
  geom_map(
    dat = world_map, map = world_map, aes(map_id = region),
    fill = "white", color = "#7f7f7f", size = 0.25
  ) +
  geom_map(map = world_map, aes(map_id = country_name, fill = n), size = 0.25) +
  scale_fill_gradient(low = "#fff7bc", high = "#cc4c02", name = "Total Cases") +
  expand_limits(x = world_map$long, y = world_map$lat) + 
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
panel.background = element_blank()) + 
  theme(axis.title = element_blank(),
        axis.ticks = element_blank(),
        axis.text = element_blank())

The result looks like this:

But I actually want something like this:

Do you have ideas how to generate such a map? Thank you very much!

yes, sorry, that's the dataframe on top! – Ane Nov 01 '22 at 13:18 — Ane, Nov 01 '22 at 13:18

score 1 · Answer 1 · answered Nov 01 '22 at 13:34

Here's a hack, not sure how awesome it is:

transform(trend_country_freq,                                            # NEW
  txt = sprintf("%s (%i)", country_name, n),                             #
  vj = -1.2 * seq(nrow(trend_country_freq))                              #
) |>                                                                     #
  ggplot() +                                                             # CHANGED
  geom_map(
    dat = world_map, map = world_map, aes(map_id = region),
    fill = "white", color = "#7f7f7f", size = 0.25
  ) +
  geom_map(map = world_map, aes(map_id = country_name, fill = n), size = 0.25) +
  scale_fill_gradient(low = "#fff7bc", high = "#cc4c02", name = "Total Cases") +
  expand_limits(x = world_map$long, y = world_map$lat) + 
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
panel.background = element_blank()) + 
  theme(axis.title = element_blank(),
        axis.ticks = element_blank(),
        axis.text = element_blank()) +
  geom_text(aes(label = txt, vjust = vj), x = -Inf, y = -Inf, hjust = 0) # NEW

score 1 · Accepted Answer · answered Nov 01 '22 at 13:42

We can simply write the text on as a geom layer:

ggplot(trend_country_freq) +
  geom_map(
    dat = world_map, map = world_map, aes(map_id = region),
    fill = "white", color = "#7f7f7f", size = 0.25
  ) +
  geom_map(map = world_map, aes(map_id = country_name, fill = n), size = 0.25) +
  scale_fill_gradient(low = "#fff7bc", high = "#cc4c02", name = "Total Cases") +
  expand_limits(x = world_map$long, y = world_map$lat) + 
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
        panel.background = element_blank()) + 
  theme(axis.title = element_blank(),
        axis.ticks = element_blank(),
        axis.text = element_blank()) +
  geom_text(aes(label = paste0(country_name, ' (', n, ')'), 
                x = rep(c(-50, 50), each = 4)[-8],
                y = rep(seq(-90, -120, -10), 2)[-8]),
            hjust = 0)

score 1 · Answer 3 · answered Nov 01 '22 at 13:44

Another option:

library(tidyverse)
library(maps)


p1 <- trend_country_freq |>
  mutate(lab = paste0(country_name, " (", n, ")")) |>
  ggplot() +
  geom_map(
    dat = world_map, map = world_map, aes(map_id = region),
    fill = "white", color = "#7f7f7f", size = 0.25
  ) +
  geom_map(map = world_map, aes(map_id = country_name, fill = n, color = lab), size = 0.25) +
  scale_fill_gradient(low = "#fff7bc", high = "#cc4c02", name = "Total Cases") +
  scale_color_manual(values = rep(NA, 7), name = "")+
  expand_limits(x = world_map$long, y = world_map$lat) + 
  theme(panel.grid.major = element_blank(), 
        panel.grid.minor = element_blank(),
        panel.background = element_blank(),
        axis.title = element_blank(),
        axis.ticks = element_blank(),
        axis.text = element_blank(),
        legend.key = element_blank()) + 
  guides(color = guide_legend(direction='horizontal',label.position = "left",
                              override.aes = list(fill = NA, color = NA)))


guide_color <- cowplot::get_legend(p1 + guides(color = "none"))

cowplot::plot_grid(p1 + 
            guides(fill = "none") + 
            theme(legend.position = "bottom"), 
          guide_color, 
          ncol = 2, rel_widths = c(.85, .15))

ggplot add country names in legend below geom_map

3 Answers3