Notes on mapping sp objects with ggplot2

ggplot2_map.R

library(ggplot2)
library(maptools)
library(mapproj)
library(ggthemes)
library(sp)
library(raster)
library(rgeos)
library(RColorBrewer)

# Get administrative boundaries as SpatialPolygonsDataFrame
crc <- raster::getData(name = "GADM", download = TRUE, 
                       path = "data",
                       country = "CR",
                       level = 2)

# Crop
new.ext <- raster::extent(c(-86, -82, 8, 11.25))
crc <- raster::crop(crc, new.ext)

# Polygon IDs to merge original SpatialPolygonsDataFrame object with newly
# fortified data.frame.
crc$id <- 1:nrow(crc)
# Fortify SpatialPolygonsDataFrame object for ggplot2
crc.df <- ggplot2::fortify(crc)
# Merge spatial attributes to fortified data.frame
crc.df <- merge(crc.df, crc, by = "id")

# Plot
ggplot(data = crc.df) +
  geom_polygon(aes(x = long, y = lat, group = group, fill = NAME_1)) +
  geom_path(aes(x = long, y = lat, group = group), colour = "white", size = 0.25) +
  scale_fill_brewer(palette = "Set3") +
  labs(title = "Costa Rica", fill = "Canton") +
  coord_map() +
  theme_minimal()