In rstudio/leaflet: Create Interactive Web Maps with the JavaScript 'Leaflet' Library

Shiny

There are two wrapper functions leafletOutput() and renderLeaflet() in this package for using Leaflet maps in shiny. The function leafletProxy() allows you to manipulate a map after it has been rendered.

UI Layers

The UI elements markers and popups are supported via addMarkers() and addPopups(), respectively. In the example below, we add a marker with a custom icon, and a popup:

leaflet() %>% addTiles() %>%
  addMarkers(174.7690922, -36.8523071, icon = icons(
    iconUrl = 'https://cran.rstudio.com/Rlogo.jpg',
    iconWidth = 40, iconHeight = 40
  )) %>%
  addPopups(174.7690922, -36.8523071, 'R was born here!')

Raster Layers

Currently tile layers are supported via addTiles(). By default, the OpenStreetMap tiles are used, and you can certainly use other tiles of your choice.

A live demo of many tile sets is available here. Note that some tile set providers require you to register. See the project page for more information.

leaflet() %>%
  addTiles(
    'http://server.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer/tile/{z}/{y}/{x}',
    attribution = 'Tiles © Esri — Esri, DeLorme, NAVTEQ, TomTom, Intermap, iPC, USGS, FAO, NPS, NRCAN, GeoBase, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), and the GIS User Community') %>%
  setView(-93.65, 42.0285, zoom = 17)

Vector Layers

Vector layers contain elements of vector graphics, such as circles, rectangles, and polylines, etc. All vector layer functions have the arguments lng and lat, with additional arguments specifying the attributes of the graphical elements. Note the terminology is slightly different with R graphics. For example, the border of elements is controlled by the argument stroke (e.g., leaflet::addRectangles(stroke = FALSE) is like graphics::rect(border = NA)), the color argument only specifies the color of the border (in base R, col/color often means the fill color), and the weight argument is like lwd in base R graphics.

set.seed(123)
m = leaflet() %>% addTiles()
rand_lng = function(n = 10) rnorm(n, -93.65, .01)
rand_lat = function(n = 10) rnorm(n, 42.0285, .01)

# circles (units in metres)
m %>% addCircles(rand_lng(50), rand_lat(50), radius = runif(50, 10, 200))

# circle markers (units in pixels)
m %>% addCircleMarkers(rand_lng(50), rand_lat(50), color = '#ff0000')
m %>% addCircleMarkers(rand_lng(100), rand_lat(100), radius = runif(100, 5, 15))

# rectangles
m %>% addRectangles(
  rand_lng(), rand_lat(), rand_lng(), rand_lat(),
  color = 'red', fill = FALSE, dashArray = '5,5', weight = 3
)

# polylines
m %>% addPolylines(rand_lng(50), rand_lat(50), fill = FALSE)

# polygons
m %>% addPolygons(
  c(rand_lng(3), NA, rand_lng(4), NA, rand_lng(5)),
  c(rand_lat(3), NA, rand_lat(4), NA, rand_lat(5)),
  color = c('red', 'green', 'blue')
)

Other Layers

GeoJSON is a JSON format for encoding geographic data structures such as points, lines, and polygons. The function addGeoJSON() allows us to add a GeoJSON layer to the map, and the layer data is normally represented as an R list. For example, the GeoJSON data

var MPoint = {
  "type": "MultiPoint",
  "coordinates": [ [100.0, 0.0], [101.0, 1.0] ]
};

can be represented in R as

MPoint = list(
  type = 'MultiPoint',
  coordinates = rbind(c(100.0, 0.0), c(101.0, 1.0))
)

You can pass this list to addGeoJSON() to draw two points on the map.

For a GeoJSON feature layer, you can use the style element in the properties list to define its style, and the popup element in properties to define the popup text. Here is an example:

m = leaflet() %>% addCircles(lat = 1:26, lng = 1:26, popup = LETTERS)
shapes = list(
  list(
    type = 'Feature',
    properties = list(
      popup = 'Here are some markers!'
    ),
    geometry = list(
      type = 'MultiPoint',
      coordinates = cbind(10:1, 1:10)
    )
  ),
  list(
    type = 'Feature',
    properties = list(
      style = list(color = 'red', fillColor = 'yellow'),
      popup = 'Here is a polygon, or perhaps a flower...'
    ),
    geometry = list(
      type = 'Polygon',
      coordinates = list(26 + 10 * t(sapply(seq(0, 2 * pi, length = 10), function(x) {
        c(cos(x), sin(x))
      })))
    )
  )
)
m %>% addGeoJSON(shapes)

rstudio/leaflet documentation built on April 15, 2024, 7:04 a.m.