使用纬度和经度向量在R中查找步行距离

Question

Hi I have a series of homes and series of rail stations. I want to calculate the walking distance from each home (n=1718) to each station (n=11). I know google limits you to 2000 obs per day, so I would do all home obs to 1 station. My data looks like this:

Home data:                      

        longitude   latitude            
    1   -76.27769   36.86308
    2   -76.29188   36.87556
    3   -76.26982   36.86628
    4   -76.27455   36.86894

    Station Data
        Longitude   Latitude
    1   -76.30377   36.85945
    2   -76.29490   36.85395
    3   -76.28896   36.85156
    4   -76.28989   36.84719
    5   -76.28579   36.84568

I found a code like this, but it sums up the distance for every home rather than the distance for each individual home.I'm pretty new to R...help!

  `distHoras <- function(origin, destination){

  origin <- gsub(",", "", origin)
  origin <- gsub(" ", "+", origin)
  origin <- paste("origins=", origin, sep = "")

  destination <- gsub(",", "", destination)
  destination <- gsub(" ", "+", destination)
  destination <- paste("destination=", paste(destination, 
                                               collapse = "|"), sep = "")


  mode4url <- paste("mode=", 'walking', sep = "")
  lang4url <- paste("language=", 'en-EN', sep = "")
  sensor4url <- paste("sensor=", tolower(as.character(FALSE)), 
                      sep = "")
  posturl <- paste(origin, destination, mode4url, sensor4url, 
                   sep = "&")
  url_string <- paste("http://maps.googleapis.com/maps/api/distancematrix/json?", 
                      posturl, sep = "")
  url_string <- URLencode(url_string)
  connect <- url(url_string)
  tree <- fromJSON(paste(readLines(connect), collapse = ""))
  close(connect)
  rapply(tree$rows,I)
}`

I get output like this

distHoras('origin', 'destination')
 elements.distance.text elements.distance.value 
             "1,253 km"               "1252635" 
 elements.duration.text elements.duration.value 
       "9 days 8 hours"                "804659" 
        elements.status 
                   "OK" 

Answer 1

Something like this??

google.dist <- function(from,to,mode="walking") {
  require(httr)
  require(XML)
  url    <- "https://maps.googleapis.com/maps/api/distancematrix/xml"
  origin <- paste(with(from,paste(latitude,longitude,sep=",")),collapse="|")
  dest   <- paste(with(to,paste(latitude,longitude,sep=",")),collapse="|")
  response <- GET(url,query=list(origins=origin,destinations=dest,mode=mode))
  doc      <- content(response,type="text/xml")
  status   <- sapply(doc["//row/element/status"],xmlValue)
  if(any(status!="OK")) warning("Error Status on some routes")
  distance <- sapply(doc["//row/element/distance/value"],xmlValue)
  data.frame(expand.grid(to=1:nrow(to),from=1:nrow(from)),distance=as.numeric(distance))
}
google.dist(Home,Station)
#    to from distance
# 1   1    1     3275
# 2   2    1     2494
# 3   3    1     2163
# 4   4    1     2548
# 5   5    1     2212
# 6   1    2     2539
# 7   2    2     2950
# 8   3    2     3288
# 9   4    2     3815
# 10  5    2     4034
# ...

This uses the Google Distance Matrix API with XML output. The returned data frame has the row numbers of the to and from data frames and the distance in meters between them. The API is documented here . Please note carefully the terms of use .