如何从Google Maps API获取驾驶时间？

Question

假设平均速度为65 km/h,我使用以下函数估算行驶一定距离的时间(以小时为单位):

distHoras <- function(origin, destination){
  xml.url <- paste0('http://maps.googleapis.com/maps/api/distancematrix/xml?origins=',
                    origin, '&destinations=', destination, '&mode=driving&sensor=false')
  xmlfile <- xmlParse(getURL(xml.url))
  dist <- xmlValue(xmlChildren(xpathApply(xmlfile,"//distance")[[1]])$value)
  distance <- as.numeric(sub(" km", "", dist))
  time <- (distance / 1000) / 65
  return(time)
}

我如何调整此函数以使其直接产生时间,因此我不需要进行65 km/h的假设,从而得到更好的估计？阅读文档后,我尝试将'distance'切换为'duration',但它没有用.我可能错过了一些简单的东西,但我对使用API​​很新,并且被所有文本所淹没.感谢任何帮助!

Answer 1

你在找这个:

library(ggmap)
from <- 'Paris'
to <- 'London'
mapdist(from,to,mode='driving')
 from     to      m      km    miles seconds  minutes    hours
1 Paris London 454416 454.416 282.3741   18283 304.7167 5.078611

mapdist使用Google地图计算地图距离.

为了回答你的问题,我认为使用json版本的谷歌API比使用谷歌API更容易(甚至推荐).

这里有一个快速版本RJSONIO.即使我建议你使用上面的功能.无需进行任何转换,因为结果已经是几小时.

library(RJSONIO)
distHoras <- function(origin, destinations){

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

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


mode4url <- paste("mode=", 'driving', sep = "")
lang4url <- paste("language=", 'en-EN', sep = "")
sensor4url <- paste("sensor=", tolower(as.character(FALSE)), 
                   sep = "")
posturl <- paste(origin, destinations, 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)
}

现在你测试它:

distHoras('Paris','London')
 elements.distance.text elements.distance.value  elements.duration.text 
               "454 km"                "454416"        "5 hours 5 mins" 
elements.duration.value         elements.status 
                "18283"                    "OK"