R/geo_code.R

In ropensci/stplanr: Sustainable Transport Planning

#' Convert text strings into points on the map
#'
#' Generate a lat/long pair from data using Google's geolocation API.
#'
#' @param address Text string representing the address you want to geocode
#' @param base_url The base url to query
#' @param return_all Should the request return all information returned by Google Maps?
#'  The default is `FALSE`: to return only two numbers: the longitude and latitude, in that order
#' @param service Which service to use? Nominatim by default
#' @param pat Personal access token
#' @family nodes
#' @export
#' @examples
#' \dontrun{
#' geo_code(address = "Hereford")
#' geo_code("LS7 3HB")
#' geo_code("hereford", return_all = TRUE)
#' # needs api key in .Renviron
#' geo_code("hereford", service = "google", pat = Sys.getenv("GOOGLE"), return_all = TRUE)
#' }
geo_code <- function(address,
                     service = "nominatim",
                     base_url = "https://maps.google.com/maps/api/geocode/json",
                     return_all = FALSE,
                     pat = NULL) {
  if (service == "nominatim") {
    if (base_url == "https://maps.google.com/maps/api/geocode/json") {
      base_url <- "https://nominatim.openstreetmap.org"
    }
    place_name <- address
    query <- list(q = place_name, format = "json")
    if (!return_all) {
      query <- c(query, limit = 1)
    }

    q_url <- httr::modify_url(base_url, query = query)
    res <- httr::GET(q_url)
    txt <- httr::content(res,
      as = "text", encoding = "UTF-8",
      type = "application/xml"
    )
    obj <- jsonlite::fromJSON(txt)
    res_df <- data.frame(lon = obj$lon, lat = obj$lat, name = obj$display_name)
    lon_lat <- as.numeric(c(lon = obj$lon[1], lat = obj$lat[1]))
  } else {
    query <- list(address = address, sensor = "false")
    if (!is.null(pat)) {
      query <- c(query, key = pat)
    }
    u <- httr::modify_url(base_url, query = query)
    res <- jsonlite::fromJSON(u)
    if (res$status == "OVER_QUERY_LIMIT") {
      stop(res$error_message)
    }

    res_df <- jsonlite::flatten(res$results)
    lon_lat <- c(
      lon = res_df$geometry.location.lng,
      lat = res_df$geometry.location.lat
    )
  }

  if (return_all) {
    return(res_df)
  } else {
    return(lon_lat)
  }
}