Georouting with Rome2rio's API

As I was looking for transit routes for a trip, I stumbled on the Rome2Rio website, which provides tons of results when you query for a trip. It provides directions for several travel modes (flights, trains/buses, driving), and it currently gathers transit info from more providers than Google Maps.

The great thing is they also provide an API, so it's quite straightforward to access their data from R.

Just sign up for an API key on their website, and the following few lines are what you need for a first exploration.

library(RJSONIO)
r2rK <- "<your-API-key-here>"
r2rS <- "<server-address-here>"
 
from <- "<origin-location-here>"
to <- "<destination-location-here>"
 
url_string <- URLencode(paste0("http://", r2rS, "/api/1.2/json/Search?key=", r2rK, "&oName=", from, "&dName=", to, "&currency=EUR"))
 
trip <- fromJSON(paste(readLines(url_string), collapse = ""))

Created by Pretty R at inside-R.org


You need to provide your key and the server address (both provided by Rome2Rio when you sign up), and the origin and destination (simply type a city name, it will be geocoded!).

Check the API documentation if you need help to understand what's inside the trip object.
Note that paths are encoded Google Maps style... but you already know how to deal with that!

ggmap + animation = fly from Bologna to Copenhagen

This is something that one should do with something different than R.
I was looking for a free tool for creating a video from Google Maps: my goal was to input a start location, an end location, and obtaining a video zooming out from the start location then zooming in to the end location.

Not having found anything of my liking, I turned to R and a couple of its packages: ggmap and animation.

Surprisingly I did not need too many lines to get something close to the desired results.
Here's what I have done.

# load the packages
library(animation)
library(ggmap)
 
# you need ffmpeg.exe installed to obtain an .mp4 video!
# tell R where to find it on your PC
oopts <- ani.options(ffmpeg = "~your/path/to/ffmpeg.exe")
 
# starting location
startLoc <- "Aeroporto Marconi, Bologna, Italy"
# destination
endLoc <- "Kastrup Airport, Denmark"
 
# minimum level of detail (how high do you want to fly?)
minDetail <- 4
 
# maximum level of detail 
maxDetail <- 18
 
# convert location do lat/lon coordinates
startCoord <- geocode(startLoc)
endCoord <- geocode(endLoc)
 
# save video in .mp4 format (it takes a while to finish!)
saveVideo({
  # from ground to sky...
  for(i in maxDetail:minDetail){
    map <- get_map(location=c(startCoord$lon, startCoord$lat), zoom=i, maptype="satellite")
    print(ggmap(map, extent="device"))
  }  
  # ...from sky to ground
  for(i in minDetail:maxDetail){
    map <- get_map(location=c(endCoord$lon, endCoord$lat), zoom=i, maptype="satellite")
    print(ggmap(map, extent="device"))
  }
}, video.name="BLQ_CPH.mp4", other.opts = "-b 1200k"  # set the file name and the video bitrate
          , outdir="~my/video/folder")  # set the folder where you want to save the video

Created by Pretty R at inside-R.org


And here's a sample result, taking us from Bologna Airport to Kastrup Airport, near Copenhagen.

 I'd certainly like to have a smoother animation, but for that some more rolling-up-the-sleeves is needed!

Feel free to tell me what you think and to improve the code.

Google Maps API - decoding polylines for drawing routes

What happens when ggplot2 and GoogleMaps have babies?
Answer: the ggmap package, by David Kahle and Hadley Wickam.

A few weeks ago, the mapdist function in the above package happened to be very useful to me at work.
The magic it does is calculating distances between locations. And you can specify if you want the driving, walking or bicycling distance.

You know what happens when you show people a cat who can sing? They say "well, but he can't play the piano!"
That's me. In fact I wondered why there was no option for distance using public transit.

I looked at Google API documentation and got all the info I needed. It's just a matter of building the right URL and you get a JSON file that is easily read by R.

The JSON contains all one would look for, including distance and time required to cover it for all legs.
But my attention was caught by lines that looked like this:

[1] "es~mGe|scAEXpCBbHHtAE|ATpFnB`DjA~B~@tDlAbBh@p@R^F\\??HBNDLJJPBLCLIDKDQ?UEQAEPEhBk@bI}CRG@BB@HDJ?JEHKFM?GbAc@`DqAfA]xBo@dAKh@KfA]xAu@pA_AzAo@\\Mj@[XQrAkAxAwAzAiAf@St@Wl@ENER?n@?d@Fr@RlAp@h@LN?\\G`@[lAiA|@cAf@o@v@o@^SlBg@v@O^AZCn@?j@F`ATdAd@n@T^@f@Al@IvASvAc@jCwAv@W|Bi@f@QhAq@n@k@X_@Zq@xAaF|@mChAqCpCgHRi@Lm@Jm@PcAJ[h@e@rGgC\\KJ@f@FXLh@\\Zl@JRAB?F?LDP@DDDHFH@JAHEFKDM@OAQEMCC?g@Jm@tAkCdAqA\\WpCyA`Ay@Z_@Zc@TMtA[hEs@n@Kh@SbBmAfAUpGZhBBp@AVEbAa@dHyCjB}@nCqAfKyDnCoAlA_@|A_@~AWnAe@pAy@^U`Be@xGmAnBWbFc@pDSfJo@tIm@fBCnBDjBTzBj@bBn@d@JbANlCGpB]vAa@dAe@lBw@xAk@fA]^Gn@IfDKpBUhJuB~AG`A@lBHr@NRJn@^p@v@T\\x@jBfCnGh@~ApAtC`ChFtDrK\\z@n@t@h@h@f@VdAXnAD~BBjCL|@LpBv@zAx@nAkCENoEoBmDiBaC}AcBuAk@k@eAiA{AqBeR_]umG_aLqC_C_D}ByBuAmBcAyDiBgCaAeDeAaB_@iB[{BUsEQcFBmDP{r@bGsDTqA@cCKmC]iCs@iBs@mAo@a|Au}@cEmBsAi@yC_AcGmAaCYmCSoCIcC?cEL}V|AsBFoCGcD_@{\\yFcBQ_x@}EkBQgB[iAYcC_AwAu@iAu@}b@{\\uCcC{BwBwB_Cwb@gg@qC}CeDwCsD_CaCeAgBm@o^wJmh@kNoCm@{Bc@iG}@sIq@mGQ_NFyoAfBqDJoBRsB`@o@PgC`AqBdA_BfAsAhAwAvAiAvAkBrCmBxDw@pBeAfDmOlg@sFnPgQtl@_@bBq@rDwA`Kw@hGu@`Hs@tHgAdPg@bDJBdBsBB@tAVLBBc@ZkDf@}EZ_DjBf@HHF@^H^P~@X|B`@xHzAxFpAtDp@`HrA~GrA~FbA"

Created by Pretty R at inside-R.org

Again, it's all explained in Google API's documentation. All those funny looking characters are the coordinates of the route after going through an encoder.
I promptly found online some decoding functions written in Javascript (I can't retrieve the links anymore, so apologies to the authors for not crediting them—I'll try to make up for this,) and rolled up my sleeves to translate them in R.

Here's the decoding function I have come up with:

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
}

Created by Pretty R at inside-R.org




I tested the decodeLine function on my home-to-work route.

# set the origin, destination and travel mode
# if travel mode is "transit" you need to specify a departure (or arrival) time
origin <- "Sasso Marconi, Italy"
destination <- "Bologna, Italy"
travelMode <- "transit"
departureTime <- Sys.time() #I want to leave now!
 
# build the URL
baseUrl <- "http://maps.googleapis.com/maps/api/directions/json?"
origin <- gsub(" ", "+", origin)
destination <- gsub(" ", "+", destination)
finalUrl <- paste(baseUrl
                  , "origin=", origin
                  , "&destination=", destination
                  , "&sensor=false"
                  , "&mode=", travelMode
                  , "&departure_time=", as.integer(departureTime)
                  , sep = "")
 
# get the JSON returned by Google and convert it to an R list
url_string <- URLencode(finalUrl)
trip <- fromJSON(paste(readLines(url_string), collapse = ""))
 
# get the encoded coordinates for the full trip
tripPathEncoded <- trip$routes[[1]]$overview_polyline$points
tripPathEncoded
 
[1] "es~mGe|scAEXpCBbHHtAE|ATpFnB`DjA~B~@tDlAbBh@p@R^F\\??HBNDLJJPBLCLIDKDQ?UEQAEPEhBk@bI}CRG@BB@HDJ?JEHKFM?GbAc@`DqAfA]xBo@dAKh@KfA]xAu@pA_AzAo@\\Mj@[XQrAkAxAwAzAiAf@St@Wl@ENER?n@?d@Fr@RlAp@h@LN?\\G`@[lAiA|@cAf@o@v@o@^SlBg@v@O^AZCn@?j@F`ATdAd@n@T^@f@Al@IvASvAc@jCwAv@W|Bi@f@QhAq@n@k@X_@Zq@xAaF|@mChAqCpCgHRi@Lm@Jm@PcAJ[h@e@rGgC\\KJ@f@FXLh@\\Zl@JRAB?F?LDP@DDDHFH@JAHEFKDM@OAQEMCC?g@Jm@tAkCdAqA\\WpCyA`Ay@Z_@Zc@TMtA[hEs@n@Kh@SbBmAfAUpGZhBBp@AVEbAa@dHyCjB}@nCqAfKyDnCoAlA_@|A_@~AWnAe@pAy@^U`Be@xGmAnBWbFc@pDSfJo@tIm@fBCnBDjBTzBj@bBn@d@JbANlCGpB]vAa@dAe@lBw@xAk@fA]^Gn@IfDKpBUhJuB~AG`A@lBHr@NRJn@^p@v@T\\x@jBfCnGh@~ApAtC`ChFtDrK\\z@n@t@h@h@f@VdAXnAD~BBjCL|@LpBv@zAx@nAkCENoEoBmDiBaC}AcBuAk@k@eAiA{AqBeR_]umG_aLqC_C_D}ByBuAmBcAyDiBgCaAeDeAaB_@iB[{BUsEQcFBmDP{r@bGsDTqA@cCKmC]iCs@iBs@mAo@a|Au}@cEmBsAi@yC_AcGmAaCYmCSoCIcC?cEL}V|AsBFoCGcD_@{\\yFcBQ_x@}EkBQgB[iAYcC_AwAu@iAu@}b@{\\uCcC{BwBwB_Cwb@gg@qC}CeDwCsD_CaCeAgBm@o^wJmh@kNoCm@{Bc@iG}@sIq@mGQ_NFyoAfBqDJoBRsB`@o@PgC`AqBdA_BfAsAhAwAvAiAvAkBrCmBxDw@pBeAfDmOlg@sFnPgQtl@_@bBq@rDwA`Kw@hGu@`Hs@tHgAdPg@bDJBdBsBB@tAVLBBc@ZkDf@}EZ_DjBf@HHF@^H^P~@X|B`@xHzAxFpAtDp@`HrA~GrA~FbA"
 
 
# decode the encoded coordinates
tripPathCoords <- decodeLine(tripPathEncoded)
head(tripPathCoords)
 
       lat      lon
1 44.39875 11.24819
2 44.39878 11.24806
3 44.39805 11.24804
4 44.39659 11.24799
5 44.39616 11.24802
6 44.39569 11.24791
 
# draw a map
library(ggmap)
map <- get_map(location = "Bologna, Italy")
ggmap(map) +
  geom_path(aes(lon, lat), data=tripPathCoords, lwd = 2)

Created by Pretty R at inside-R.org

Here it is! Actually I take a shorter path when I commute, but the one shown here is not a fault of the decodeLine function—for some reason the train line I use is not available on GoogleMaps (despite it's run by the same company running the displayed one!)

While writing this post, I discovered someone else had already invented this wheel, so you can use Diego Valle's code if you prefer.