leaflet: Create a Leaflet map widget

Description

This function creates a Leaflet map widget using htmlwidgets. The widget can be rendered on HTML pages generated from R Markdown, Shiny, or other applications.

Usage

leaflet(data = NULL, width = NULL, height = NULL, padding = 0)

Arguments

data

a data object (currently supported objects are matrices, data frames, and spatial objects from the sp package of classes SpatialPoints, SpatialPointsDataFrame, Polygon, Polygons, Spatial

width

the width of the map

height

the height of the map

padding

the padding of the map

Value

A HTML widget object, on which we can add graphics layers using %>% (see examples).

Details

The data argument is only needed if you are going to reference variables in this object later in map layers. For example, data can be a data frame containing columns latitude and longtitude, then we may add a circle layer to the map by

leaflet(data) %>%
addCircles(lat = ~latitude, lng = ~longtitude)

, where the variables in the formulae will be evaluated in the data.

Examples

Run this code

library(leaflet)
m = leaflet() %>% addTiles()
m  # a map with the default OSM tile layer

# set bounds
m %>% fitBounds(0, 40, 10, 50)

# move the center to Snedecor Hall
m = m %>% setView(-93.65, 42.0285, zoom = 17)
m

# popup
m %>% addPopups(-93.65, 42.0285, 'Here is the <b>Department of Statistics</b>, ISU')
rand_lng = function(n = 10) rnorm(n, -93.65, .01)
rand_lat = function(n = 10) rnorm(n, 42.0285, .01)

# use automatic bounds derived from lng/lat data
m = m %>% clearBounds()

# popup
m %>% addPopups(rand_lng(), rand_lat(), 'Random popups')

# marker
m %>% addMarkers(rand_lng(), rand_lat())
m %>% addMarkers(
  rand_lng(), rand_lat(), popup = paste('A random letter', sample(LETTERS, 10))
)

Rlogo = file.path(R.home('doc'), 'html', 'logo.jpg')
m %>% addMarkers(
  174.7690922, -36.8523071, icon = list(
    iconUrl = Rlogo, iconSize = c(100, 76)
  ), popup = 'R was born here!'
)

m %>% addMarkers(rnorm(30, 175), rnorm(30, -37), icon = list(
  iconUrl = Rlogo, iconSize = c(25, 19)
))

m %>% addMarkers(
  c(-71.0382679, -122.1217866), c(42.3489054, 47.6763144), icon = list(
    iconUrl = 'http://www.rstudio.com/wp-content/uploads/2014/03/blue-125.png'
  ), popup = c('RStudio @ Boston', 'RStudio @ Seattle')
)


# circle (units in metres)
m %>% addCircles(rand_lng(50), rand_lat(50), radius = runif(50, 50, 150))

# circle marker (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))

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

# polyline
m %>% addPolylines(rand_lng(50), rand_lat(50))

# polygon
m %>% addPolygons(rand_lng(), rand_lat(), layerId = 'foo')

# geoJSON
seattle_geojson = list(
  type = "Feature",
  geometry = list(
    type = "MultiPolygon",
    coordinates = list(list(list(
      c(-122.36075812146,  47.6759920119894),
      c(-122.360781646764, 47.6668890126755),
      c(-122.360782108665,  47.6614990696722),
      c(-122.366199035722, 47.6614990696722),
      c(-122.366199035722,  47.6592874248973),
      c(-122.364582509469, 47.6576254522105),
      c(-122.363887331445,  47.6569107302038),
      c(-122.360865528129, 47.6538418253251),
      c(-122.360866157644,  47.6535254473167),
      c(-122.360866581103, 47.6533126275176),
      c(-122.362526540691,  47.6541872926348),
      c(-122.364442114483, 47.6551892850798),
      c(-122.366077719797,  47.6560733960606),
      c(-122.368818463838, 47.6579742346694),
      c(-122.370115159943,  47.6588730808334),
      c(-122.372295967029, 47.6604350102328),
      c(-122.37381369088,  47.660582362063),
      c(-122.375522972109, 47.6606413027949),
      c(-122.376079703095,  47.6608793094619),
      c(-122.376206315662, 47.6609242364243),
      c(-122.377610811371,  47.6606160735197),
      c(-122.379857378879, 47.6610306942278),
      c(-122.382454873022,  47.6627496239169),
      c(-122.385357955057, 47.6638573778241),
      c(-122.386007328104,  47.6640865692306),
      c(-122.387186331506, 47.6654326177161),
      c(-122.387802656231,  47.6661492860294),
      c(-122.388108244121, 47.6664548739202),
      c(-122.389177800763,  47.6663784774359),
      c(-122.390582858689, 47.6665072251861),
      c(-122.390793942299,  47.6659699214511),
      c(-122.391507906234, 47.6659200946229),
      c(-122.392883050767,  47.6664166747017),
      c(-122.392847210144, 47.6678696739431),
      c(-122.392904778401,  47.6709016021624),
      c(-122.39296705153, 47.6732047491624),
      c(-122.393000803496,  47.6759322346303),
      c(-122.37666945305, 47.6759896300663),
      c(-122.376486363943,  47.6759891899754),
      c(-122.366078869215, 47.6759641734893),
      c(-122.36075812146,  47.6759920119894)
    )))
  ),
  properties = list(
    name = "Ballard",
    population = 48000,
    # You can inline styles if you want
    style = list(
      fillColor = "yellow",
      weight = 2,
      color = "#000000"
    )
  ),
  id = "ballard"
)
m %>% setView(-122.36075812146, 47.6759920119894, zoom = 13) %>% addGeoJSON(seattle_geojson)


# use the Dark Matter layer from CartoDB
leaflet() %>% addTiles('http://{s}.basemaps.cartocdn.com/dark_all/{z}/{x}/{y}.png',
  attribution = paste(
    '© <a href="http://openstreetmap.org">OpenStreetMap</a> contributors',
    '© <a href="http://cartodb.com/attributions">CartoDB</a>'
  )
) %>% setView(-122.36, 47.67, zoom = 10)

# provide a data frame to leaflet()
categories = LETTERS[1:10]
df = data.frame(
  lat = rand_lat(100), lng = rand_lng(100), size = runif(100, 5, 20),
  category = factor(sample(categories, 100, replace = TRUE), levels = categories),
  value = rnorm(100)
)
m = leaflet(df) %>% addTiles()
m %>% addCircleMarkers(~lng, ~lat, radius = ~size)
m %>% addCircleMarkers(~lng, ~lat, radius = runif(100, 4, 10), color = c('red'))

# Discrete colors using the "RdYlBu" colorbrewer palette, mapped to categories
RdYlBu = colorFactor("RdYlBu", domain = categories)
m %>% addCircleMarkers(~lng, ~lat, radius = ~size,
  color = ~RdYlBu(category), fillOpacity = 0.5)

# Continuous colors using the "Greens" colorbrewer palette, mapped to value
greens = colorNumeric("Greens", domain = NULL)
m %>% addCircleMarkers(~lng, ~lat, radius = ~size,
  color = ~greens(value), fillOpacity = 0.5)

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