🌐 Get country information (name, iso3, continent) from geospatial coordinates (latitude and longitude) in R without contacting an external API

coords2country.R

library(sp)
library(rworldmap)

#' Get country from coordinates
#' based on: https://stackoverflow.com/questions/14334970/convert-latitude-and-longitude-coordinates-to-country-name-in-r/14342127#14342127
#'
#' @param lng Contains the longitude in degrees
#' @param lat Contains the latitude in degrees
#' @param export What to return, options: 'name' => country name (default), 'iso3' => ISO3 country code, 'continent6' => continent (6 continent model), 'continent7' => continent (7 continent model), 'raw' => whole spatial indices object
#'
#' @return Country information selected in 'export' (defaults to country name)
#' @export
#'
#' @examples
#' coords2country(lat = c(52.3667), lng = c(4.8945))
#' coords2country(lat = c(52.3667), lng = c(4.8945), export = 'iso3')
coords2country = function(lat, lng, export = 'name') {
  points <- data.frame(lng, lat) # create point dataframe as requested with longitude then latitude
  
  countriesSP <- getMap(resolution='low')
  #countriesSP <- getMap(resolution='high') #you could use high res map from rworldxtra if you were concerned about detail
  
  # convert our list of points to a SpatialPoints object
  # pointsSP = SpatialPoints(points, proj4string=CRS(" +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +towgs84=0,0,0"))
  
  #setting CRS directly to that from rworldmap
  pointsSP = SpatialPoints(points, proj4string=CRS(proj4string(countriesSP)))  
  
  
  # use 'over' to get indices of the Polygons object containing each point 
  indices = over(pointsSP, countriesSP)
  
  switch (export,
    name = indices$ADMIN, # return the ADMIN names of each country
    iso3 = indices$ISO3, # returns the ISO3 code 
    continent6 = indices$continent, # returns the continent (6 continent model)
    continent7 = indices$REGION, # returns the continent (7 continent model)
    raw = indices, # return the raw indices object with everything
  )
}