Convert latitude and longitude coordinates to country name in R

Question

I have a list of latitude and longitude coordinates, and wish to find out which country they all reside in.

I modified an answer from this question about lat-long to

Answer 1

You can use my geonames package to lookup from the http://geonames.org/ service:

> GNcountryCode(51.5,0)
$languages
[1] "en-GB,cy-GB,gd"

$distance
[1] "0"

$countryName
[1] "United Kingdom of Great Britain and Northern Ireland"

$countryCode
[1] "GB"

> GNcountryCode(44.5,20)
$languages
[1] "sr,hu,bs,rom"

$distance
[1] "0"

$countryName
[1] "Serbia"

$countryCode
[1] "RS"

Get it from r-forge because I'm not sure I bothered to release it to CRAN:

https://r-forge.r-project.org/projects/geonames/

Yes, it depends on an external service, but at least it knows what happened to communism... :)

Answer 2

Thanks for the carefully constructed question. It required just a couple of line changes to be able to use rworldmap (containing up-to-date countries) see below. I'm not an expert on CRS but I don't think the change I had to make to the proj4string makes any difference. Others might like to comment on that.

This worked for me & gave :

> coords2country(points)
[1] United Kingdom     Belgium            Germany            Austria           
[5] Republic of Serbia

All the best, Andy

library(sp)
library(rworldmap)

# The single argument to this function, points, is a data.frame in which:
#   - column 1 contains the longitude in degrees
#   - column 2 contains the latitude in degrees
coords2country = function(points)
{  
  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)

  # return the ADMIN names of each country
  indices$ADMIN  
  #indices$ISO3 # returns the ISO3 code 
  #indices$continent   # returns the continent (6 continent model)
  #indices$REGION   # returns the continent (7 continent model)
}