Googleway Vignette

Setting / Using keys

All the API functions have a key argument which you can use to provide your API key. Alternatively, you can use set_key() to set the key once, and make it available for all further API calls.

If you use one key for all API calls you can just provide the key argument (it will automatically get set as your default key).

If you use many different keys, you can specify which API they are for in the api argument.

library(googleway)
## not specifying the api will add the key as your 'default'
key <- "my_api_key"
set_key(key = key)
google_keys()

## Google API keys
##  -  default : my_api_key 
##  -  map :  
##  -  directions :  
##  -  distance :  
##  -  elevation :  
##  -  geocode :  
##  -  places :  
##  -  find_place :  
##  -  place_autocomplete :  
##  -  place_details :  
##  -  reverse_geocode :  
##  -  roads :  
##  -  streetview :  
##  -  timezone :

## specifying the specific API will only make that key available for that API.
clear_keys() ## clear any previously set keys
key <- "my_api_key"
set_key(key = key, api = "directions")
google_keys()

## Google API keys
##  -  default :  
##  -  map :  
##  -  directions : my_api_key 
##  -  distance :  
##  -  elevation :  
##  -  geocode :  
##  -  places :  
##  -  find_place :  
##  -  place_autocomplete :  
##  -  place_details :  
##  -  reverse_geocode :  
##  -  roads :  
##  -  streetview :  
##  -  timezone :

Text

For a text search you are required to provide a search_string

For example, here’s a query for “restaurants in Melbourne”

res <- google_places(search_string = "Restaurants in Melbourne, Australia",
                     key = key)

## View the names of the returned restaurantes, and whether they are open or not

cbind(res$results$name, res$results$opening_hours)

                                            res$results$name open_now weekday_text
1                                               Vue de monde     TRUE         NULL
2                                                      ezard    FALSE         NULL
3                                                     MoVida     TRUE         NULL
4                           Flower Drum Restaurant Melbourne     TRUE         NULL
5                                             The Press Club    FALSE         NULL
6                                                       Maha     TRUE         NULL
7                                                  Bluestone       NA         NULL
8                                                  Chin Chin     TRUE         NULL
9                                               Taxi Kitchen     TRUE         NULL
10                                           Max on Hardware     TRUE         NULL
11                                                    Attica    FALSE         NULL
12                                       Nirankar Restaurant    FALSE         NULL
13                                                  The Mill     TRUE         NULL
14                                   The Left Bank Melbourne     TRUE         NULL
15                           The Colonial Tramcar Restaurant     TRUE         NULL
16                                      Rockpool Bar & Grill     TRUE         NULL
17 Lane Restaurant Cafe & Bar - Novotel Melbourne on Collins     TRUE         NULL
18                                          Melba Restaurant     TRUE         NULL
19                                              CUMULUS INC.     TRUE         NULL
20                                    radii restaurant & bar    FALSE         NULL

A single query will return 20 results per page. You can view the next 20 results using the next_page_token that is returned as part of the initial query.

res_next <- google_places(search_string = "Restaurants in Melbourne, Australia",
                          page_token = res$next_page_token,
                          key = key)
                          
cbind(res_next$results$name, res_next$results$opening_hours)

                     res_next$results$name open_now weekday_text
1  Moshi Moshi Japanese Seafood Restaurant     TRUE         NULL
2                      Grill Steak Seafood     TRUE         NULL
3                             Conservatory     TRUE         NULL
4                                    Sarti    FALSE         NULL
5                                  Tsindos     TRUE         NULL
6                 The Cerberus Beach House     TRUE         NULL
7                   Stalactites Restaurant     TRUE         NULL
8            Hanabishi Japanese Restaurant    FALSE         NULL
9                          GAZI Restaurant     TRUE         NULL
10                           Om Vegetarian    FALSE         NULL
11                           Shark Fin Inn     TRUE         NULL
12                           Om Vegetarian     TRUE         NULL
13                 The Atlantic Restaurant     TRUE         NULL
14                                  Takumi     TRUE         NULL
15                              Pei Modern       NA         NULL
16                 Bamboo House Restaurant     TRUE         NULL
17                 Byblos Bar & Restaurant     TRUE         NULL
18                              Waterfront     TRUE         NULL
19                                   No 35     TRUE         NULL
20                        Bistro Guillaume     TRUE         NULL

Nearby

For a nearby search you are required to provide a location as a pair of latitude/longitude coordinates. You can refine your search by providing a keyword and / or a radius.

res <- google_places(location = c(-37.918, 144.968),
                    keyword = "Restaurant",
                    radius = 5000,
                    key = key)


cbind(res$results$name, res$results$opening_hours)
#                         res$results$name open_now weekday_text
# 1                              Melbourne       NA         NULL
# 2              Quest Brighton on the Bay     TRUE         NULL
# 3                         Brighton Savoy    FALSE         NULL
# 4  Caroline Serviced Apartments Brighton     TRUE         NULL
# 5      The Buckingham Serviced Apartment       NA         NULL
# 6                      Sandringham Hotel     TRUE         NULL
# 7               Indian Palace Restaurant     TRUE         NULL
# 8                       Elsternwick Park     TRUE         NULL
# 9                         Brown Cow Cafe     TRUE         NULL
# 10              Bok Choy Chinese Cuisine    FALSE         NULL
# 11                          Marine Hotel     TRUE         NULL
# 12                          Daily Planet     TRUE         NULL
# 13                         Riva St Kilda     TRUE         NULL
# 14                         New Bay Hotel     TRUE         NULL
# 15          Flight Centre North Brighton     TRUE         NULL
# 16              Vintage Cellars Brighton     TRUE         NULL
# 17                   Palace Brighton Bay     TRUE         NULL
# 18                       Brighton Toyota     TRUE         NULL
# 19                            Sportsgirl     TRUE         NULL
# 20                           Saint Kilda       NA         NULL

Snap to Roads

The snap to roads function takes up to 100 GPS points collected along a route and returns the points snapped to the most likely roads that were travelled along.

df_path <- read.table(text = "lat lon
-35.27801 149.12958
-35.28032 149.12907
-35.28099 149.12929
-35.28144 149.12984
-35.28194 149.13003
-35.28282 149.12956
-35.28302 149.12881
-35.28473 149.12836
", header = T, stringsAsFactors = F)


res <- google_snapToRoads(df_path = df_path, key = key)

res$snappedPoints
  location.latitude location.longitude originalIndex                     placeId
1         -35.27800           149.1295             0 ChIJr_xl0GdNFmsRsUtUbW7qABM
2         -35.28032           149.1291             1 ChIJOyypT2hNFmsRZBtscGL0htw
3         -35.28101           149.1292             2 ChIJv5r0smlNFmsR5nunau79Fv4
4         -35.28147           149.1298             3 ChIJ601MoWlNFmsR5mvkfPp2ovA
5         -35.28194           149.1300             4 ChIJ601MoWlNFmsR5mvkfPp2ovA
6         -35.28282           149.1296             5 ChIJaUpThGlNFmsRMHWxoH7EOsc
7         -35.28313           149.1289             6 ChIJWSb8ImpNFmsRp_4JAxJFE1A
8         -35.28473           149.1283             7 ChIJtWxAZmpNFmsRlbUCkc6VtnA

The result includes the column originalIndex. This is a zero-based index that indicates which of the input coordinates has been snapped to the given location.latitude/location.longitude coordinates. So in this example, originalIndex 0 is the first row of df_path, originalIndex 1 is the second row of df_path, and so on.

Nearest Roads

The nearest roads function takes up to 100 independent coordinates and returns the closest road segment for each point.

df_points <- read.table(text = "lat lon
60.1707 24.9426
60.1708 24.9424
60.1709 24.9423", header = T)

res <- google_nearestRoads(df_points, key = key)

res$snappedPoints
  location.latitude location.longitude originalIndex                     placeId
1          60.17070           24.94272             0 ChIJNX9BrM0LkkYRIM-cQg265e8
2          60.17081           24.94271             1 ChIJNX9BrM0LkkYRIM-cQg265e8
3          60.17091           24.94270             2 ChIJNX9BrM0LkkYRIM-cQg265e8

Markers

Markers and circles can be used to show points on the map.

In this example I’m using the tram_stops data set provided with googleway.

You can specify a column in the data.frame to use to populate a popup info_window that will be displayed when clicking on a maker. The info window can display any valid HTML, as demonstrated in this Stack Overflow answer.

df <- tram_stops
df$info <- paste0("<b>Stop Name: </b>", df$stop_name)

map_key <- "your_api_key"
google_map(data = df, key = map_key) %>%
  add_markers(lat = "stop_lat", lon = "stop_lon", info_window = "info")

Marker Info Window

Heatmap

You can create a heatmap using Google’s Heatlayer.

google_map(data = tram_stops, key = map_key) %>%
  add_heatmap(lat = "stop_lat", lon = "stop_lon", option_radius = 0.0025)

Heatmap

There are a few options you can configure to change how the heatmap is plotted, for example changing the colours, and weight associated with each point in the data set

## the colours can be any of those given by colors()
tram_stops$weight <- 1:nrow(tram_stops)

google_map(data = tram_stops, key = map_key) %>%
  add_heatmap(lat = "stop_lat", lon = "stop_lon", option_radius = 0.0025,
              weight = 'weight', 
              option_gradient = c("plum1", "purple1", "peachpuff"))

Heatmap Colour

Polyline

Polylines in Google Maps are formed from a set of latitude/longitude coordinates, encoded into a polyline string.

Both the add_polylines() and add_polygons() functions in googleway can plot the encoded polyline to save the amount of data set to the browser. (They can also plot coordinates, but this is often slower).

To draw a line on a map you use the add_polylines() function. This function takes a data.frame with at least one column of data containing the polylines, or two columns containing the series of lat/lon coordinates.

Here we can plot the polyline we generated earlier from querying the directions from Melbourne to Sydney.

df <- data.frame(polyline = pl)

google_map(key = map_key) %>%
    add_polylines(data = df, polyline = "polyline", stroke_weight = 9)

Polyline

Polygon

A polygon represents an area enclosed by one or more polylines. Holes are denoted by defining an inner path wound in the opposite direction to the outer path.

To draw a polygon on a map use the add_polygons() function. This function takes a data.frame, where the polygons can be specified in one of three ways

• Multiple rows of latitude and longitude coordinates that specify paths, using an id and pathId value to specify the polygon that each path belongs to
• Rows of encoded polylines, using a id value to specify the polygon that each polyline represents
• Rows of nested polylines in a list column. Each row represents a polygon, and each polyline in the list represents the paths that make up the polygon.

The melbourne data set provided with googleway is a data.frame of polygons of Melbourne and the surrounding suburbs. The coordinates of the polygons are encoded in to polylines.

melbourne[melbourne$polygonId == 338 & melbourne$pathId %in% c(1, 2), ]

##     polygonId pathId     SA2_NAME             SA3_NAME             SA4_NAME
## 386       338      1 Point Nepean Mornington Peninsula Mornington Peninsula
## 387       338      2 Point Nepean Mornington Peninsula Mornington Peninsula
##     AREASQKM               polyline
## 386  67.1875 `haiFgzjrZJMJBBRIJMCCQ
## 387  67.1875 z{biFyqlrZARO@SUTOB@JL

Plotting this data is done using add_polygons()

google_map(key = "your_api_key") %>% 
  add_polygons(data = melbourne, polyline = "polyline", fill_colour = "SA4_NAME")

Melbourne Polygons

In this example I’ve specified the fill_colour to be one of the columns of the melbourne data set. The plotting functions in googleway will map the variables in the column to a given colour. The default colour scale is taken from viridisLite::viridis().

Colours & Legend

Where applicable the map layer functions provide two arguments that you can use to plot colours

• fill_colour (for colouring an area)
• stroke_colour (for colouring a line / outline of an area)

Each of those arguments can be mapped to a column of data (as in the Polygon example), or if you want to use your own colours you can either

• specify the palette using the palette argument

google_map(key = "your_api_key") %>% 
  add_polygons(data = melbourne, polyline = "polyline", fill_colour = "SA4_NAME", palette = viridisLite::inferno)

Colour Palette

• add a column of hex colour values and supply this to the plotting function

colours <- RColorBrewer::brewer.pal(9, "Set1")
melbourne$randomColour <- sample(colours, size = nrow(melbourne), replace = T)
google_map(key = "your_api_key") %>% 
  add_polygons(data = melbourne, polyline = "polyline", fill_colour = "randomColour")

Colour Column

• specify a single hex colour value to either fill_colour or stroke_colour to colour all shapes the same colour

google_map(key = "your_api_key") %>% 
  add_polygons(data = melbourne, polyline = "polyline", fill_colour = "#FF00FF")

Single Colour

Setting legend = TRUE will give you a legend

google_map(key = "your_api_key") %>% 
  add_polygons(data = melbourne, polyline = "polyline", fill_colour = "SA4_NAME", legend = T)

Legend

You can customise the legend by supplying any of the arguments in a list to the legend_options argument

• position - one of TOP_LEFT, TOP_CENTER, TOP_RIGHT, RIGHT_TOP, RIGHT_CENTER, RIGHT_BOTTOM, BOTTOM_RIGHT, BOTTOM_CENTER, BOTTOM_LEFT, LEFT_BOTTOM, LEFT_CENTER and LEFT_TOP
• css - a string of valid CSS for controlling the appearance
• title - a string to use for the title of the legend. The default is the column name mapped to the colour

If you are displaying two legends, one for stroke_colour and one for fill_colour, you can specify different options for the different colour attributes

legendOpts <- list(
  fill_colour = list(position = "TOP_RIGHT"),
  stroke_colour = list(position = "BOTTOM_LEFT", title = "SA3")
  )

google_map(key = "your_api_key") %>% 
  add_polygons(data = melbourne, polyline = "polyline", fill_colour = "SA4_NAME", stroke_colour = "SA3_NAME", legend = T, legend_options = legendOpts)

Custom Legend

Simple Features

googleway supports plotting certain geometries from sf objects (from library(sf))

• POINT and MULTIPOINT plotted with add_markers() and add_circles()
• LINESTRING and MULTILINESTRING plotted with add_polylines()
• POLYGON and MULTIPOLYGON plotted with add_polygons()

This example uses and plots the polygons from the North Carolina data set supplied with library(sf)

library(sf)
nc <- sf::st_read(system.file("shape/nc.shp", package="sf"))

google_map(data = nc) %>%
  add_polygons()

sf North Carolina

If the sf objects contains multiple geometries, you can also use the various add_* functions to add specific rows of the sf object. The mapping between the functions and the sf objects is

• add_markers() - POINT & MULTIPOINT
• add_circles() - POINT & MULTIPOINT
• add_polylines() - LINESTRING & MULTILINESTRING
• add_polygons() - POLYGON & MULTIPOLYGON

df <- data.frame(myId = c(1,1,1,1,1,1,1,1,2,2,2,2),
  lineId = c(1,1,1,1,2,2,2,2,1,1,1,2),
    lon = c(-80.190, -66.118, -64.757, -80.190,  -70.579, -67.514, -66.668, -70.579, -70, -49, -51, -70),
    lat = c(26.774, 18.466, 32.321, 26.774, 28.745, 29.570, 27.339, 28.745, 22, 23, 22, 22))

p1 <- as.matrix(df[4:1, c("lon", "lat")])
p2 <- as.matrix(df[8:5, c("lon", "lat")])
p3 <- as.matrix(df[9:12, c("lon", "lat")])

point <- sf::st_sfc(sf::st_point(x = c(df[1,"lon"], df[1,"lat"])))
multipoint <- sf::st_sfc(sf::st_multipoint(x = as.matrix(df[1:2, c("lon", "lat")])))
polygon <- sf::st_sfc(sf::st_polygon(x = list(p1, p2)))
linestring <- sf::st_sfc(sf::st_linestring(p3))
multilinestring <- sf::st_sfc(sf::st_multilinestring(list(p1, p2)))
multipolygon <- sf::st_sfc(sf::st_multipolygon(x = list(list(p1, p2), list(p3))))

sf <- rbind(
    sf::st_sf(geometry = polygon),
    sf::st_sf(geometry = multipolygon),
    sf::st_sf(geometry = multilinestring),
    sf::st_sf(geometry = linestring),
    sf::st_sf(geometry = point),
  sf::st_sf(geometry = multipoint)
)


google_map(data = sf) %>%
  add_markers() %>%
  add_polylines()

sf marker & line

GeoJSON

The geo_melbourne data set is a GeoJSON representation of a subset of the melbourne data set. You can use add_geojson to plot this data

google_map() %>%
  add_geojson(data = geo_melbourne)

Geojson

By default add_geojson() will apply any styles included in the GeoJSON file. In the geo_melbourne data you can see the styles fillColor, strokeColor and strokeWeight

substr(geo_melbourne[1], 1, 300)

## {"type":"FeatureCollection","features":[{"type":"Feature","properties":{"SA2_NAME":"Abbotsford","polygonId":70,"SA3_NAME":"Yarra","AREASQKM":1.7405,"fillColor":"#440154","strokeColor":"#440154","strokeWeight":1},"geometry":{"type":"Polygon","coordinates":[[[144.9925232,-37.8024902],[144.9926453,-37.

You can also supply a string of JSON to style all the features in the GeoJSON

style <- '{ "fillColor" : "green" , "strokeColor" : "black", "strokeWeight" : 0.5}'
google_map(key = "your_api_key") %>%
  add_geojson(data = geo_melbourne, style = style)

Or you can use a named list to have the same effect

style <- list(fillColor = "red" , strokeColor = "blue", strokeWeight = 0.5)
google_map(key = "your_api_key") %>%
  add_geojson(data = geo_melbourne, style = style)

Drag & Drop Geojson

The function add_dragdrop() creates a map on to which you can drag & drop a GeoJSON file. There is an example of this in action on my blog

Rectangles

Rectangles can be added by supplying north, east, south and west coordinates to add_rectangles()

df <- data.frame(north = 33.685, south = 33.671, east = -116.234, west = -116.251)

google_map(key = "your_api_key") %>%
  add_rectangles(data = df, north = 'north', south = 'south',
                 east = 'east', west = 'west')

Drawing

You can create your own shapes on a map using add_drawing(). The shapes you can create are

• markers
• circles
• polygon
• polyline
• rectangle

This can be particularly useful when working with shiny as the shape information can be returned when drawing is completed.

For example, use the following code to create a shiny that enables drawing circles.

library(shiny)

ui <- fluidPage(
  google_mapOutput(outputId = "map", height = "800px")
)

server <- function(input, output){

  mapKey <- "your_map_key"
  output$map <- renderGoogle_map({
    google_map(key = mapKey) %>%
      add_drawing(drawing_modes = c("circle"))
  })


  observeEvent(input$map_circlecomplete, {
    print(input$map_circlecomplete)
  })
}
shinyApp(ui, server)

When a circle is drawin, the print(input$map_circlecomplete) function prints the following information to the console (it will vary based on where you draw the circle)

$center
$center$lat
[1] -36.80489

$center$lng
[1] 144.2889


$radius
[1] 57970.9

$bounds
$bounds$south
[1] -37.32565

$bounds$west
[1] 143.6385

$bounds$north
[1] -36.28413

$bounds$east
[1] 144.9393


$randomValue
[1] 0.3688953

KML & GeoRSS

The add_kml() function renders KML and GeoRSS elements on a Google Map. All you need to specify is a URL containing the kml data.

kmlUrl <- 'https://googlemaps.github.io/js-v2-samples/ggeoxml/cta.kml'

google_map(key = "your_api_key") %>%
  add_kml(kml_url = kmlUrl)

KML

Overlays

Overalys are objects on the map that are tied to latitude/longitude coordinates, so they move when you drag or zoom the map.

You need to supply the lat/lon coordinates to the north (lat), south (lat), east (lon) and west (lon) arguments, and a URL to the overlay.

google_map(key = "your_api_key") %>%
  add_overlay(north = 40.773941, south = 40.712216, east = -74.12544, west = -74.22655,
               overlay_url = "https://www.lib.utexas.edu/maps/historical/newark_nj_1922.jpg")

Overlay

Returning Data

One of the more powerful features of googleway mapping is the ability to return data from the maps to R using Shiny.

Data can be returned using

• clicking on the map
• panning / zooming the map
• shape / layer clicks
• editing shapes
• dragging shapes

Within the google_map() call you can pass one of two values to the event_return_type argument, “list” or “json”. This controls the type of data structure returned back to R from Shiny.

Clicking on the map

Data can be retrieved from the map by clicking on it and “observing” the clicks.

The structure of the observed event is

• input$<map_id>_map_click

where

• <map_id> is the id of the output map element (see example)
• map_click is the event being observed

library(shiny)
ui <- fluidPage(
 google_mapOutput('myMap')
)
server <- function(input, output){
 output$myMap <- renderGoogle_map({
   google_map(key = "your_api_key", event_return_type = "list")
 })
 observeEvent(input$myMap_map_click, {
    print(input$myMap_map_click)
 })
}
shinyApp(ui, server)

Clicking on the map in this example will return the following fields

$id
[1] "myMap"

$lat
[1] -37.68382

$lon
[1] 145.08

$centerLat
[1] -37.9

$centerLon
[1] 144.5

$zoom
[1] 8

$randomValue
[1] 0.4043373

Similarly, observing input$myMap_bounds_changed will observe panning the map, and input$myMap_zoom_changed will observe zooming the map.

Shape / layer clicks

Data can be retrieved from shapes by clicking on them and “observing” the clicks.

The structure of the observed event is

• input$<map_id>_<shape>_click

where

• <map_id> is the id of the output map element (see example)
• <shape> is the shape being clicked (e.g. polygon, polyline, circle, etc)
• click is the event being observed

library(shiny)
ui <- fluidPage(
 google_mapOutput('map')
)
server <- function(input, output){
 output$map <- renderGoogle_map({
   google_map(key = "your_api_key", event_return_type = "list") %>%
     add_polygons(data = melbourne, polyline = "polyline")
 })
 observeEvent(input$map_polygon_click, {
    print(input$map_polygon_click)
 })
}
shinyApp(ui, server)

Clicking on one of the polygons in this example will return the fields

$id
[1] 22

$lat
[1] -38.16911

$lon
[1] 144.6872

$outerPath
[1] "dlsgFyduq..." ## truncated

$allPaths
$allPaths[[1]]
[1] "dlsgFyduqZ..." ## truncated


$randomValue
[1] 0.5917599

$layerId
[1] "defaultLayerId"

Editing & Dragging Shapes

The shape layers that have a editable argument also return data when the shape is edited.

In this case you would observe input$<map_id>_<shape>_edited

Similarly, when shapes are dragged you would observe input$<map_id>_<shape>_dragged