Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
How to use Google's API with R

Using Google Maps API and R

This script uses RCurl and RJSONIO to download data from Google's API to get the latitude, longitude, location type, and formatted address

library(RCurl)
library(RJSONIO)
library(plyr)

Build a URL to access the API:

url <- function(address, return.call = "json", sensor = "false") {
  root <- "http://maps.google.com/maps/api/geocode/"
  u <- paste(root, return.call, "?address=", address, "&sensor=", sensor, sep = "")
  return(URLencode(u))
}

Function to parse the results:

geoCode <- function(address,verbose=FALSE) {
  if(verbose) cat(address,"\n")
  u <- url(address)
  doc <- getURL(u)
  x <- fromJSON(doc,simplify = FALSE)
  if(x$status=="OK") {
    lat <- x$results[[1]]$geometry$location$lat
    lng <- x$results[[1]]$geometry$location$lng
    location_type  <- x$results[[1]]$geometry$location_type
    formatted_address  <- x$results[[1]]$formatted_address
    return(c(lat, lng, location_type, formatted_address))
    Sys.sleep(0.5)
  } else {
    return(c(NA,NA,NA, NA))
  }
}

Test with one address

address <- geoCode("The White House, Washington, DC")

First two items are the latitude and longitude coordinates, then the location type and formatted address

address

We can use Plyr to geocode a vector with addresses

address <- c("The White House, Washington, DC","The Capitol, Washington, DC")
locations  <- ldply(address, function(x) geoCode(x))
names(locations)  <- c("lat","lon","location_type", "formatted")
head(locations)

The following are the different location types:

  • "ROOFTOP" indicates that the returned result is a precise geocode for which we have location information accurate down to street address precision.
  • RANGE_INTERPOLATED" indicates that the returned result reflects an approximation (usually on a road) interpolated between two precise points (such as intersections). Interpolated results are generally returned when rooftop geocodes are unavailable for a street address.
  • GEOMETRIC_CENTER" indicates that the returned result is the geometric center of a result such as a polyline (for example, a street) or polygon (region).
  • APPROXIMATE" indicates that the returned result is approximate.

For more info on Google Maps API check here

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment