如何获取ggmap路径数据以跟踪道路路径
问题描述:
我正在使用ggmap路由函数来计算和显示使用D.C. Capital Bikeshare数据的数百条路线。我成功地通过一个小问题来解决这个问题,路线并不遵循道路,特别是弯曲的道路(见下面的屏幕截图)。有没有办法让我的代码遍历所有更详细的路径?如何获取ggmap路径数据以跟踪道路路径
library(tidyverse)
library(ggmap)
# Example dataset
feb_14 <- read.csv('https://raw.githubusercontent.com/smitty1788/Personal-Website/master/dl/CaBi_Feb_2017.csv', stringsAsFactors = FALSE)
# Subset first 300 rows, keep start and end Lat/Long strings
start<-c(feb_14[1:300, 14])
dest<-c(feb_14[1:300, 15])
# df of individual routes
routes <- tibble(
start,
dest)
# Function to calculate route
calculationroute <- function(startingpoint, stoppoint) {
route(from = startingpoint,
to = stoppoint,
mode = 'bicycling',
structure = "route")}
# Calculate route path for all individual trips
calculatedroutes <- mapply(calculationroute,
startingpoint = routes$start,
stoppoint = routes$dest,
SIMPLIFY = FALSE)
# Unlist and merge in single dataframe
do.call(rbind.data.frame, lapply(names(calculatedroutes), function(x) {
cbind.data.frame(route=x, calculatedroutes[[x]], stringsAsFactors=FALSE)
})) -> long_routes
# create map with routes
basicmap <- get_map(location = 'washingtondc',
zoom = 13,
maptype = "toner-background",
source = "google",
color = "bw")
basicmap <- ggmap(basicmap)
basicmap + geom_path(data=long_routes,
aes(x=lon, y=lat, group=route), color = "red",
size=1, alpha = .4, lineend = "round")
答
答案是对decodeLine功能放入do.call创造长期路线数据帧
decodeLine <- function(encoded){
require(bitops)
vlen <- nchar(encoded)
vindex <- 0
varray <- NULL
vlat <- 0
vlng <- 0
while(vindex < vlen){
vb <- NULL
vshift <- 0
vresult <- 0
repeat{
if(vindex + 1 <= vlen){
vindex <- vindex + 1
vb <- as.integer(charToRaw(substr(encoded, vindex, vindex))) - 63
}
vresult <- bitOr(vresult, bitShiftL(bitAnd(vb, 31), vshift))
vshift <- vshift + 5
if(vb < 32) break
}
dlat <- ifelse(
bitAnd(vresult, 1)
, -(bitShiftR(vresult, 1)+1)
, bitShiftR(vresult, 1)
)
vlat <- vlat + dlat
vshift <- 0
vresult <- 0
repeat{
if(vindex + 1 <= vlen) {
vindex <- vindex+1
vb <- as.integer(charToRaw(substr(encoded, vindex, vindex))) - 63
}
vresult <- bitOr(vresult, bitShiftL(bitAnd(vb, 31), vshift))
vshift <- vshift + 5
if(vb < 32) break
}
dlng <- ifelse(
bitAnd(vresult, 1)
, -(bitShiftR(vresult, 1)+1)
, bitShiftR(vresult, 1)
)
vlng <- vlng + dlng
varray <- rbind(varray, c(vlat * 1e-5, vlng * 1e-5))
}
coords <- data.frame(varray)
names(coords) <- c("lat", "lon")
coords
}
calculatedroutes <- mapply(calculationroute,
startingpoint = routes$start,
stoppoint = routes$dest,
SIMPLIFY = FALSE)
do.call(rbind.data.frame, lapply(names(calculatedroutes), function(x) {
cbind.data.frame(route = x, decodeLine(calculatedroutes[[x]]$routes[[1]]$overview_polyline$points), stringsAsFactors=FALSE)
})) -> long_routes
尝试用'输出= “所有”''里面路线( from = startingpoint, to = stoppoint, mode ='bicycling', structure =“route”,output =“all”)' – SymbolixAU
这会导致do.call(rbind ...引发此错误。函数(...,row.name s = NULL,check.rows = FALSE,check.names = TRUE,: 参数意味着不同的行数:1,0 –
Mapzen的Valhalla是一个web服务,可以提供从点到点的路由,包括路由的GeoJSON。 https://mapzen.com/blog/valhalla-intro/。 GeoJSONio软件包显然可以使用它。 –