Remove countries' political borders from ggplot2 map - ggplot2

Question

I need to remove the political borders of the countries from the following ggplot2 map:
library(ggplot2)
world = map_data('world')
plot=ggplot() +
geom_polygon(data=world, aes(x=long, y=lat, group=group), fill='NA', color='black', size=0.2)
print(plot)
Any suggestion on how I can do this?
Thanks

Answer 1

There are two workarounds to your question:
First workaround: Using maps instead of ggplot2
library(maps)
world <- maps::map("world", fill=FALSE, plot=TRUE, interior = FALSE)
Which results in:
Second workaround: Using maps and ggplot2
library(maps)
library(magrittr)
library(maptools)
library(raster)
library(ggplot2)
#Defining a general CRS
mycrs <- "+proj=longlat +datum=WGS84 +no_defs"
#Using the original maps package, then converting map into SpatialPolygons object
world <- maps::map("world", fill=TRUE) %$%
maptools::map2SpatialPolygons(., IDs=names,proj4string=CRS(mycrs))
#The resulting map has self intersection problems so any further operation reports errors; using buffers of width 0 is a fast fix
while(rgeos::gIsValid(world)==FALSE){
world <- rgeos::gBuffer(world, byid = TRUE, width = 0, quadsegs = 5, capStyle = "ROUND")
}
#Dissolving polygon's limits
world <- raster::aggregate(world)
#Plotting. I add theme_void to your code to erase any axis, etc
ggplot() +
geom_polygon(data = world, aes(x=long, y=lat, group=group), fill='NA', color='black', size=0.2)+
theme_void()
The result:
Hope it helps

Answer 2

The rnaturalearth package offers an easier way to make world maps in ggplot2 now.
library(ggplot2)
library(rnaturalearth)
#Mapping for coastlines
coast <- ne_coastline(scale = "small", returnclass = "sf")
ggplot(data = coast) + geom_sf() + theme_classic()
#Optional - apply a fill to the continents
world <- ne_countries(scale = "small", returnclass = "sf")
ggplot(data = world) +
geom_sf(color = "#E5E5E5", fill = "#E5E5E5") +
geom_sf(data = coast) + theme_classic()