r - Adding scale bar to ggplot map

Question

I've produced this map in ggplot2:

library(maptools); library(ggplot2)
data(wrld_simpl)
world <- fortify(wrld_simpl)
worldUk <- subset(world, id=="GBR")
ggplot() +
geom_path(aes(long, lat, group=group), data=worldUk, color="black", fill=NA) +
  coord_equal()

Using photoshop, I've added a scale bar to the map. How can I add a similar scale bar using ggplot2? This post adds a scale bar, but the bar doesn't refer to distance: scale bar and north arrow on map-ggplot2

Answer 1

There is a package called ggsn, which allows you to customize the scale bar and north arrow.

ggplot() +
  geom_path(aes(long, lat, group=group), data=worldUk, color="black", fill=NA) +
  coord_equal() +
  ggsn::scalebar(worldUk, dist = 100, st.size=3, height=0.01, dd2km = TRUE, model = 'WGS84')