leaflet

Leaflet是一个用于交互式地图的开源JavaScript库。这个R包可以很容易地从R创建Leaflet地图。
语法：leaflet通过管道操作%>%叠加图层作图。

基本用法

您使用以下基本步骤创建Leaflet地图：

  1. 通过leaflet()调用创建地图小部件。
  2. 通过使用层功能（例如，addTiles，addMarkers，addPolygons）添加层到地图，来修改窗口小部件的地图。
  3. 根据需要重复步骤2。
  4. 打印地图小部件以显示它。
library(leaflet)
m <- leaflet() %>%
  addTiles() %>%  # Add default OpenStreetMap map tiles
  addMarkers(lng=174.768, lat=-36.852, popup="The birthplace of R")
m  # Print the map

Map Widget：地图控件

已整理的组件用法链接

Initialization (初始化)

函数 说明
leaflet() 标准函数
center Initial geographic center of the map
zoom Initial map zoom level
minZoom Minimum zoom level of themap
maxZoom Maximum zoom level of thema 
leaflet(data = NULL,width = NULL, height = NULL, 
  padding = 0,options = leafletOptions())

Map Methods (作图方法)

函数 说明
setView(map,lng,lat,zoom, options = list()) ) 设置地图视图的中心和缩放级别
fitBounds(map, lng1, lat1, lng2, lat2) 设定边界经纬度
clearBounds(map) 清除边界，从地图元素中自动设定

Data Object (数据对象)

leaflet()图层和map图层都有一个data参数，用来接收空间数据，data的格式如下：

  • Base R : data.frame对象
 df <-data.frame(lat = ..., lng= ... ) 
leaflet(df) %>% addTiles() %>% addCircles()

  • sp package library(sp) Useful functions
    SpatialPoints, SpatialLines, SpatialPolygons, ...

  • maps package library(maps)

mapStates <-map("state", fill = TRUE, plot = FALSE)
leaflet(mapStates) %>% 
  addTiles() %>% 
  addPolygons(fillColor = topo.colors(10, alpha = NULL), stroke = FALSE)`

示例

library(maps)
mapStates = map("state", fill = TRUE, plot = FALSE)
leaflet(data = mapStates) %>% addTiles() %>%
  addPolygons(fillColor = topo.colors(10, alpha = NULL), stroke = FALSE)

Basemaps：底图

addTiles() 添加地图瓦片，默认OpenStreetMap图块
addProviderTiles(map, provider) 添加第三方图块
addWMSTiles() 添加WMS (Web Map Service) 图块

names(providers) : 查看所有第三方图块
参数provider = c(providers$Stamen.Toner, CartoDB.Positron, Esri.NatGeoWorldMap)

Markers：标记

接收经纬度坐标latitude/longitude ，标记出icons or circles，data数据来自向量或已赋值data.frame或sp对象。

1. Icon Markers

# 添加默认标记
addMarkers(map, lng = NULL, lat = NULL,icon = NULL, 
  popup = NULL, label = NULL,clusterOptions = NULL) 

#定制标记
makeIcon/icons(iconUrl, iconWidth, iconHeight, iconAnchorX, iconAnchorY, shadowUrl, shadowWidth, shadowHeight, ... ) 

# 创建图表列表，通过位置或名称从该列表中进行选择
iconList(icon1= makeIcon(…), icon2= makeIcon(…)) 

# 自定义标记
addAwesomeMarkers, makeAwesomeIcon, awesomeIcons, awesomeIconList

addMarkers()参数：
icon, popup : 点击时要显示的消息
label : 鼠标静止时显示的信息
clusterOptions = markerClusterOptions() : 大量标记时集群显示选项

示例 1

# 默认markers
data(quakes) # Show first 20 rows from the `quakes` dataset
leaflet(data = quakes[1:20,]) %>% addTiles() %>%
  addMarkers(~long, ~lat, popup = ~as.character(mag), label = ~as.character(mag))

示例 2

quakes1 <- quakes[1:10,]

leafIcons <- icons(
  iconUrl = ifelse(quakes1$mag < 4.6,
    "http://leafletjs.com/examples/custom-icons/leaf-green.png",
    "http://leafletjs.com/examples/custom-icons/leaf-red.png"
  ),
  iconWidth = 38, iconHeight = 95,
  iconAnchorX = 22, iconAnchorY = 94,
  shadowUrl = "http://leafletjs.com/examples/custom-icons/leaf-shadow.png",
  shadowWidth = 50, shadowHeight = 64,
  shadowAnchorX = 4, shadowAnchorY = 62
)

leaflet(data = quakes1) %>% addTiles() %>%
  addMarkers(~long, ~lat, icon = leafIcons)

示例 3

leaflet(quakes) %>% addTiles() %>% addMarkers(
  clusterOptions = markerClusterOptions()
)

2. Circle Markers

addCircleMarkers(map, color, radius, stroke, opacity, ... )
#设定原标记的颜色，半径，点击，模糊度

示例 4

# Create a palette that maps factor levels to colors
pal <- colorFactor(c("navy", "red"), domain = c("ship", "pirate"))

leaflet(df) %>% addTiles() %>%
  addCircleMarkers(
    radius = ~ifelse(type == "ship", 6, 10),
    color = ~pal(type),
    stroke = FALSE, fillOpacity = 0.5
  )

Popups and Labels：弹出窗口和标签

addPopups(map, lng, lat, ...content..., options)#添加标准弹出窗口
# options = popupOptions(closeButton=FALSE)

addMarkers(..., popup, ... ) #在markers中添加窗口
addMarkers(..., label, labelOptions... ) #在markers中添加标签 
# labelOptions = labelOptions(noHide,	textOnly,	textsize,	direction,	style) 

addLabelOnlyMarkers() #只添加标签

示例

content <- paste(sep = "<br/>",
  "<b><a href='http://www.samurainoodle.com'>Samurai Noodle</a></b>",
  "606 5th Ave. S",
  "Seattle, WA 98138"
)

leaflet() %>% addTiles() %>%
  addPopups(-122.327298, 47.597131, content,
    options = popupOptions(closeButton = FALSE)
  )

cl

Lines and Shapes：线条和几何形状

Polygons and Polylines

addPolygons(map, lng = NULL, lat = NULL ,
  color = "03F", weight = 5, opacity = 0.5,    #线条颜色，粗细，不透明度
  fill = TRUE, fillColor = color, fillOpacity = 0.2, 
  popup = NULL,highlightOptions,...)
# highlightOptions(color, weight=2, bringToFront=TRUE) 高亮图形
# 使用rmapshaper::ms_simplify 简化复杂的图形

Circles and Rectangles

addCircles(map,lng = NULL,lat = NULL,radius = 10,...)# 圆形，半径以米为单位
addRectangles(map, lng1, lat1, lng2, lat2,...)# 对角线参数指定矩形

示例

cities <- read.csv(textConnection("
City,Lat,Long,Pop
Boston,42.3601,-71.0589,645966
Hartford,41.7627,-72.6743,125017
New York City,40.7127,-74.0059,8406000
Philadelphia,39.9500,-75.1667,1553000
Pittsburgh,40.4397,-79.9764,305841
Providence,41.8236,-71.4222,177994
"))

leaflet(cities) %>% addTiles() %>%
  addCircles(lng = ~Long, lat = ~Lat, weight = 1,
    radius = ~sqrt(Pop) * 30, popup = ~City
  )

其他组件

组件 说明
addLegend() 图例
addMeasure() 测量插件
addGraticule() 网格线
addTerminator() 日夜线
addMiniMap() 迷你地图

GeoJSON and TopoJSON

有两种方法来使用GeoJSON/TopoJSON data

  • 使用geojsonio or rgdal package 读入sp 对象
    geojsonio :: geojson_read (..., what =“ sp ”)
    rgdal :: readOGR (...,“ OGRGeoJSON ”)
  • 使用本包 addGeoJSON() and addTopoJSON() 函数
    addTopoJSON / addGeoJSON (... weight , color , fill , opacity , fillOpacity ... )
  • 另外的包RJSONIO and jsonlite 也能很快解析

Shiny Integration

UI 部分：leafletOutput(“name”)
server 部分：renderLeaflet(…)
渲染：renderLeaflet () 返回Leaflet map 对象

修改

函数举例 在serve中修改
leafletProxy() 通用修改
fitBounds(0, 0, 11, 11) 配置边界
addCircles(1:10, 1:10, layerId = LETTERS[1:10]) 添加圆形
removeShape(c(“B”, “F”)) 移除形状
clearShapes() 清除形状

Inputs/Events

  • 对象事件
    input$MAPID_OBJCATEGORY_EVENTNAME抓取事件变化的值赋给shiny变量
    OBJCATEGORY: marker, shape, geojson and topojson
    EVENTNAME: click, mouseover and mouseout.

所有这些事件都被设为NULL或list(lat,lng,id)（被触发时）

  • 地图事件
    input$MAPID_click：地图背景或basemap被敲击时提供list(lat,lng)
    input$MAPID_bounds：list(north,east,south,west)
    input$MAPID_zoom：zoom level

leafletCN

leafletCN是一个基于leaflet的中国扩展包, 里面保存了一些适用于中国的区域划分数据以及一些有帮助的函数, 地理区划数据来源于github的[geojson-map-china][chinamap]项目. 数据细分到县级市.
[chinamap]: https://github.com/longwosion/geojson-map-china

自带地图数据（GeoJSON）

regionNames(mapName)返回地图的区域名，细分到县(world,china,city,…)

绘图（leaflet封装）

demomap (mapName) 传入地图名绘制地图，等同于(leaflet包， leaflet+addTiles +addPolygons)

示例

demomap("上海")

geojsonMap(dat, mapName) 底图+填色地图，dat赋值data.frame(regions,values)

sh = regionNames("上海")
dat = data.frame(name = sh,value = rnorm(length(sh)))
geojsonMap(dat,"上海")

辅助函数

amap(map)高德地图底图，方便leaflet包调用
read.geoShape(geojson) 读取一个geojson的对象，保存成sp对象
leafletGeo(mapName,dat = NULL) 用地图名和数据框把地图和数值组合在一起

system.file("geojson/china.json",package = "leafletCN")%>%
  read.geoShape()%>%
  plot()