zumbov2 / walkalytics

An R wrapper for the walkalytics API

Walkalytics

This R package is an interface to the Walkalytics API that calculates the walking isochrone for a source location based on map data. To get an API key, you need to register at https://dev.walkalytics.com/signin. With the free starter account, you can make up to 100 calls a week to the API. More information (geographical availability of the service etc.) can be found here.

Update 2021-02-04: The [Walkalytics API] is no longer available.

Installation

Version 0.1.0 is on CRAN, and you can install it by:

install.packages("walkalytics")

For regularly updated version (latest: 0.1.0), install from GitHub:

install.packages("devtools")
devtools::install_github("zumbov2/walkalytics")

Example 1: Albert's life in Aarau

Young Albert failed the entrance examination for ETH Zurich. The 16-year-old is now to move to Aarau to complete his secondary schooling. He doesn't know the town yet and is thinking about buying a bike for his everday life. Let's help Albert decide. He doesn't want to have to walk longer than 10 minutes.

We define the blokes's most important points-of-interest and call the walkalytics API with the function isochrome_pois(). We take Albert's future address as the source location. The function pois_walktimes() processes the API response object in such a way that the estimated walking times (in seconds) between the source location and the points-of-interest are returned.

# Define Albert's points-of-interest 
places <- data.frame(id = c("School", "Railway Station", "Affenkasten (Pub)", "Zurlindeninsel (River Island)"),
                     x = c(895737, 896297, 895620, 895840),
                     y = c(6006558, 6006247, 6006171, 6007080))

# Call Walkalytics API and extract walking times to points-of-interest
isochrone_pois(x = 896552, y = 6006578, epsg = 3857, pois = places, key = key) %>% pois_walktimes()

# A tibble: 4 x 4
  id                            walktime      x       y
  <chr>                            <int>  <int>   <int>
1 Railway Station                    184 896297 6006247
2 School                             348 895737 6006558
3 Zurlindeninsel (River Island)      470 895840 6007080
4 Affenkasten (Pub)                  500 895620 6006171

Lucky Albert. He can save his money. Read more about Albert's life here.

Example 2: More details please

We can go one step further and extract high-resolution walking times. For this we use the function isochrone_esri(), which returns a response object that contains a base64-encoded gzipped Esri ASCII grid with walking times for every pixel. By using the function esri_to_sgdf(), we can convert the encoded Esri ASCII grid to an object of class SpatialGridDataFrame or we use pixel_walktimes() to directly extract walking times (in seconds) for every pixel with respect to the source location.

# Call Walkalytics API and convert response object to SpatialGridDataFrame
dt <- isochrone_esri(x = 896552, y = 6006578, epsg = 3857, key = key) %>% esri_to_sgdf()

# Call Walkalytics API and extract walking times for every pixel
dt2 <- isochrone_esri(x = 896552, y = 6006578, epsg = 3857, key = key) %>% pixel_walktimes()

dt can then be displayed graphically using image()

require(viridisLite)
image(dt, col = magma(10, direction = -1))

Example 3: Public transportation stops for Switzerland

Beside the isochrone API Walkalytics also offers the possibility of querying nearby public transportation stops. The query works in the almost same way as the previous examples.

# Call the Walkalytics pubtrans API and extract the walking times to the stations
pubtrans_ch_nearby(x = 8.528872, y = 47.382902, max_walktime = 10, key = key) %>% get_stops()  

# A tibble: 7 x 8
  name                          walktime station_category latitude longitude coordinates_type transport_category id     
  <chr>                            <dbl> <chr>            <chr>    <chr>     <chr>            <chr>              <chr>  
1 Zürich, Röntgenstrasse            1.30 3                8.529264 47.381932 WGS84            Bus                8591322
2 Zürich, Limmatplatz               3.40 2                8.531623 47.384600 WGS84            Bus_Tram           8591257
3 Zürich, Militär-/Langstrasse      4.40 2                8.527627 47.379600 WGS84            Bus                8591277
4 Zürich, Quellenstrasse            6.10 2                8.528753 47.386740 WGS84            Bus_Tram           8591306
5 Zürich, Kanonengasse              7.70 3                8.530306 47.378468 WGS84            Bus                8591219
6 Zürich, Museum für Gestaltung     8.50 2                8.534937 47.382121 WGS84            Bus_Tram           8591282
7 Zürich, Dammweg                   9.20 2                8.526392 47.388490 WGS84            Bus_Tram           8591110

More

Walkalytics also offers the possibility to save isochrones with freely selectable break values as PNG images (isochrone_png() %>% save_png()).

Happy testing!