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rggplot2dplyrmapsborder

How can I remove Antarctica borders from a ggplot2 map?

Suppose I want to create a world map, with borders. I do not need Antarctica in the plot, so I filter it from the map data.

library(dplyr)
library(ggplot2)
library(maps)

world_map <- map_data("world") %>% 
  filter(region != "Antarctica")

However, if I add borders() to the plot, it shows up again because the function takes the border data straight from the maps package, including Antarctica.

ggplot()+
  geom_polygon(data = world_map, aes(x = long, y = lat, group = group))+
  borders()

With Antarctica borders

Is there a way to exclude it, maybe using the regionsargument? I could not find a way, except for playing around with ylim = c(-55, 90), as suggested in another post, which works. However, it also seems like a very crude solution that might work in this specific case, but not in most others.

With ylim

Solution

  • You can use colour = and fill = to define your map borders and fill colours:

    library(dplyr)
library(ggplot2)
library(maps)

world_map <- map_data("world") %>% 
  filter(region != "Antarctica")

ggplot() +
  geom_polygon(data = world_map,
               aes(x = long, y = lat, group = group),
               colour = "black",
               fill = "grey")

    result

    However, note that geom_polygon is not the best geom to use when working with geospatial data. If you want a map that conforms to geographical norms, the easiest way is to use the rnaturalearth package. The ne_countries() world dataset is an sf object, and comes with a defined CRS. As such, you can use geom_sf() to plot it. It's a much more robust approach and it's simpler too as ggplot2 does a lot of the 'heavy lifting' for you e.g. no need to declare x and y aesthetics:

    library(rnaturalearth)

world_map1 <- ne_countries() %>% 
  filter(sovereignt != "Antarctica")

ggplot() +
  geom_sf(data = world_map1,
          colour = "black",
          fill = "grey")

    result2

    To ensure the y-axis text is plotted, and the northern and southern-most features aren't touching the edge of the plot (which personally I don't like), you could use something like:

    ggplot() +
  geom_sf(data = world_map1,
          colour = "black",
          fill = "grey") +
  coord_sf(expand = FALSE) +
  scale_y_continuous(limits = c(-58, 90))