Geocode and reverse geocode your data using, R, JSON and Google Maps’ Geocoding API

March 20, 2012

(This article was first published on All Things R, and kindly contributed to R-bloggers)

Geocode and reverse geocode your data using, R, JSON and Google Maps' Geocoding API

To geocode and reverse geocode my data, I use Google's Geocoding service which returns the geocoded data in a JSON. I will recommend that you register with Google Maps API and get a key if you have large amount of data and would do repeated geo coding.

Geocode:

getGeoCode <- function(gcStr) {
library("RJSONIO") #Load Library
gcStr <- gsub(' ','%20',gcStr) #Encode URL Parameters
#Open Connection
connectStr <- paste('http://maps.google.com/maps/api/geocode/json?sensor=false&address=',gcStr, sep="")
con <- url(connectStr)
data.json <- fromJSON(paste(readLines(con), collapse=""))
close(con)
#Flatten the received JSON
data.json <- unlist(data.json)
if(data.json["status"]=="OK") {
lat <- data.json["results.geometry.location.lat"]
lng <- data.json["results.geometry.location.lng"]
gcodes <- c(lat, lng)
names(gcodes) <- c("Lat", "Lng")
return (gcodes)
}
}
geoCodes <- getGeoCode("Palo Alto,California")
> geoCodes
Lat Lng
"37.4418834" "-122.1430195"

Reverse Geocode:
reverseGeoCode <- function(latlng) {
latlngStr <- gsub(' ','%20', paste(latlng, collapse=","))#Collapse and Encode URL Parameters
library("RJSONIO") #Load Library
#Open Connection
connectStr <- paste('http://maps.google.com/maps/api/geocode/json?sensor=false&latlng=',latlngStr, sep="")
con <- url(connectStr)
data.json <- fromJSON(paste(readLines(con), collapse=""))
close(con)
#Flatten the received JSON
data.json <- unlist(data.json)
if(data.json["status"]=="OK")
address <- data.json["results.formatted_address"]
return (address)
}
address <- reverseGeoCode(c(37.4418834, -122.1430195))
> address
results.formatted_address
"668 Coleridge Ave, Palo Alto, CA 94301, USA"

Happy Coding!

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