osm_geocoder.R

#' osm_geocoder
#'
#' geocodes a location using OpenStreetMap.
#'
#' @param location a character string or list specifying a location of interest.
#' @return data.frame with variables lon and lat
#' @seealso \url{http://wiki.openstreetmap.org/wiki/Nominatim}

osm_geocoder <- function(location) {
  library(jsonlite)
  location<-gsub(' ', "+", location)
  url_string <- paste0('http://nominatim.openstreetmap.org/search?format=json&addressdetails=0&limit=1&q=', location)
  
  list<-sapply(url_string, fromJSON)
  lat<-NULL
  lon<-NULL
  
  if (length(url_string)>1){

  # Get Latitude
  lat<-lapply(list, '[[', "lat")
  lat<-lapply(lat, FUN = function(x){
  ifelse(is.null(x), NA, x)
    })
  lat<-unlist(lat)
  
  # Get Longitude
  lon<-lapply(list, '[[', "lon")
  lon<-lapply(lon, FUN = function(x){
  ifelse(is.null(x), NA, x)
    })
  lon<-unlist(lon)}else{
    
  names(list)<-attr(list, "dimnames")[[1]]
  
  # Get Latitude
  lat<-list$lat
  lat<-lapply(lat, FUN = function(x){
  ifelse(is.null(x), NA, x)
    })
  lat<-unlist(lat)
  
  # Get Longitude
  lon<-list$lon
  lon<-lapply(lon, FUN = function(x){
  ifelse(is.null(x), NA, x)
    })
  lon<-unlist(lon)
  }
  
  df<-data.frame(lat=lat, lon=lon) 
  rownames(df)<-NULL
  return(df)

}