Me he registrado en Google para obtener más solicitudes de distancias de tiempo de conducción. Sin embargo, Google no recoge automáticamente este "permiso" para ejecutar más de 2500 consultas al día. Adicionalmentemapdist() no tiene un argumento para integrar una clave API.

He logrado obtener una clave API a través de la consola de Google.

Traté de modificar el código sin procesar agregando clave y cambiando la línea 56, 90 y 91 de la siguiente manera:

    mapdist <- function(from, to, mode = c("driving","walking","bicycling"),
  output = c("simple","all"), messaging = FALSE, sensor = FALSE,
  language = "en-EN", override_limit = FALSE, key = "XXXX")
{

  message("by using this function you are agreeing to the terms at :")
  message("http://code.google.com/apis/maps/documentation/distancematrix/\n")

  # check parameters
  if(is.numeric(from) && length(from) == 2) from <- revgeocode(from)
  stopifnot(is.character(from))
  if(is.numeric(to) && length(to) == 2) to <- revgeocode(to)
  stopifnot(is.character(to))
  from_to_df <- data.frame(from = from, to = to, stringsAsFactors = FALSE)
  origins <- from_to_df$from
  destinations <- from_to_df$to # this ensures # from = # to
  mode <- match.arg(mode)
  output <- match.arg(output)
  stopifnot(is.logical(messaging))
  stopifnot(is.logical(sensor))


  getdists <- function(df){

    # format url
    origin <- df$from[1]
    origin <- gsub(",", "", origin)
    origin <- gsub(" ", "+", origin)
    origin <- paste("origins=", origin, sep = "")
    destinations <- df$to
    destinations <- gsub(",", "", destinations)
    destinations <- gsub(" ", "+", destinations)
    destinations <- paste("destinations=", paste(destinations, collapse = "|"), sep = "")
    mode4url <- paste("mode=", mode, sep = "")
    lang4url <- paste("language=", language, sep = "")
    sensor4url <- paste("sensor=", tolower(as.character(sensor)), sep = "")
    keyUrl <- paste("key=", key, sep = "")
    posturl <- paste(origin, destinations, mode4url, sensor4url, keyUrl, sep = "&")
    url_string <- paste("http://maps.googleapis.com/maps/api/distancematrix/json?",
      posturl, sep = "")
    url_string <- URLencode(url_string)


    # check if query is too long
    if(nchar(url_string) >= 2048){
      n <- nrow(df)
      half_df <- floor(n/2)
      return(
        rbind(
          getdists(df[half_df,]),
          getdists(df[(half_df+1):n,])
        )
      )
    }

    # check/update google query limit
    check_dist_query_limit(url_string, elems = nrow(df),
      override = override_limit, messaging = messaging)


    # distance lookup
    if(messaging) message("trying url ", url_string)
    connect <- url(url_string)
    tree <- fromJSON(paste(readLines(connect), collapse = ""))
    close(connect)

    # message user
    message(paste0("Information from URL : ", url_string))

    # label destinations - first check if all were found
    if(length(df$to) != length(tree$destination_addresses)){
      message("matching was not perfect, returning what was found.")
      names( tree$rows[[c(1,1)]] ) <- tree$destination_addresses
      output <<- "all"
      # stringdist::amatch(df$to, tree$destination_addresses, maxDist = 10)
    } else {
      names( tree$rows[[c(1,1)]] ) <- df$to
    }

    # return
    tree$rows[[c(1,1)]]
  }

  out <- dlply(from_to_df, "from", getdists)

  # return all
  if(output == "all") return(out)



  # format output
  out <-
    ldply(out, function(oneFromList){
      ldply(oneFromList, function(oneToList){
        data.frame(
          m = oneToList$distance$value,
          km = oneToList$distance$value/1000,
          miles = 0.0006214 * oneToList$distance$value,
          seconds = oneToList$duration$value,
          minutes = oneToList$duration$value / 60,
          hours = oneToList$duration$value / 3600
        )
      })
    })

  names(out) <- c("from", "to", names(out)[3:ncol(out)])

  # "simple" return
  suppressMessages(join(from_to_df, out))
}




check_dist_query_limit <- function(url_string, elems, override, messaging){
  .GoogleDistQueryCount <- NULL; rm(.GoogleDistQueryCount); # R CMD check trick

  if(exists(".GoogleDistQueryCount", .GlobalEnv)){

    .GoogleDistQueryCount <<-
      subset(.GoogleDistQueryCount, time >= Sys.time() - 24*60*60)

    # 2500 per 24 hours
    if(sum(.GoogleDistQueryCount$elements) + elems > 2500){
      message("query max exceeded, see ?mapdist.  current total = ",
        sum(.GoogleDistQueryCount$elements))
      if(!override) stop("google query limit exceeded.", call. = FALSE)
    }

    # 100 per 10 seconds
    if(with(.GoogleDistQueryCount,
      sum(elements[time >= Sys.time() - 10]) + elems > 100
    )){
      if(messaging) message("waiting 10 seconds for another 100 queries...", appendLF=F)
      Sys.sleep(10) # can do better
      if(messaging) message(" done")
    }

    # append to .GoogleDistQueryCount
    .GoogleDistQueryCount <<- rbind(.GoogleDistQueryCount,
      data.frame(time = Sys.time(),  url = url_string,
        elements = elems, stringsAsFactors = FALSE)
    )


  } else {

    .GoogleDistQueryCount <<-
      data.frame(time = Sys.time(),  url = url_string,
        elements = elems, stringsAsFactors = FALSE)

  }
}



#' Check Google Maps Distance Matrix API query limit
#'
#' Check Google Maps Distance Matrix API query limit
#'
#' @return a data frame
#' @author David Kahle \email{david.kahle@@gmail.com}
#' @seealso \url{http://code.google.com/apis/maps/documentation/distancematrix/}
#' @export
#' @examples
#' distQueryCheck()
distQueryCheck <- function(){
  .GoogleDistQueryCount <- NULL; rm(.GoogleDistQueryCount); # R CMD check trick
  if(exists(".GoogleDistQueryCount", .GlobalEnv)){
    remaining <- 2500-sum(
      subset(.GoogleDistQueryCount, time >= Sys.time() - 24*60*60)$elements
      )
    message(remaining, " distance queries remaining.")
  } else {
    remaining <- 2500
    message(remaining, " distance queries remaining.")
  }
  invisible(remaining)
}

Sin embargo, recibí este mensaje de error al ejecutar mapdist ():

by using this function you are agreeing to the terms at :
http://code.google.com/apis/maps/documentation/distancematrix/

Information from URL : http://maps.googleapis.com/maps/api/distancematrix/json?origins=NG17+7LG&destinations=CV2+2DX&mode=driving&sensor=false&key=AIzaSyBQN9Dvgfw3bXpWj_-ddluungZcDv8Y4rg
matching was not perfect, returning what was found.
Error in `*tmp*`[[c(1, 1)]] : no such index at level 1
Called from: .fun(piece, ...)
Browse[1]> results <- dput(result)
list()
Browse[1]> res_df <- do.call(rbind, results)

Tengo la sensación de que tengo que integrar esta clave en mi código en R para que Google pueda recoger mi "permiso". Un amigo me dijo que podía hacerlohttr Pero no sé mucho al respecto. ¡Realmente no sé mucho sobre codificación y agradeceré cualquier ayuda!