手动为 Leaflet 地图创建点答案

【问题标题】：Manually creating points for Leaflet map手动为 Leaflet 地图创建点
【发布时间】：2018-07-15 21:57:02
【问题描述】：

我正在创建一些点来绘制在 Leaflet-R 地图上。但是，当尝试使用 addCircles 绘制点时出现错误：

Warning: Error in derivePoints: Point data not found; please provide addCircles with data and/or lng/lat arguments

关于空间数据框的信息如下：

Simple feature collection with 3 features and 4 fields
geometry type:  POINT
dimension:      XY
bbox:           xmin: -79.48837 ymin: 43.66537 xmax: -79.29187 ymax: 43.71345
epsg (SRID):    4326
proj4string:    +proj=longlat +datum=WGS84 +no_defs

我有另一个可用的空间数据框，所有信息都相同，只是 +datum=WGS84 被替换为 +ellps=WGS84。会是这样吗？如果是这样，我该如何进行此更改？

示例代码

library(shiny)
library(leaflet)

ui <- fluidPage(
  leafletOutput("mymap")
)

server <- function(input, output, session) {

  # Create tree geometries
  tree_1g <- st_point(c(-79.2918671415814, 43.6760766531298))
  tree_2g <- st_point(c(-79.4883669334101, 43.6653747165064))
  tree_3g <- st_point(c(-79.2964680812039, 43.7134458013647))

  # Create sfc object with multiple sfg objects
  points_sfc <- st_sfc(tree_1g, tree_2g, tree_3g, crs = 4326)

  # Create tree attributes
  data <- data.frame (
    id = c(1, 2, 3),
    address = c(10, 20, 30),
    street = c("first", "second", "third"),
    tname = c("oak", "elm", "birch")
)

  tree_data <- st_sf(data, geometry = points_sfc)

  output$mymap <- renderLeaflet({
    leaflet() %>%
      addProviderTiles(providers$Stamen.Watercolor) %>%

      # Centre the map in the middle of Toronto
      setView(lng = -79.384293, 
              lat = 43.685, #43.653908, 
              zoom = 11) %>% 

      addCircles(tree_data)
  })
}

shinyApp(ui, server)

【问题讨论】：

标签： r geospatial r-leaflet

【解决方案1】：

解决方案

您需要指定data = tree_data，因为在addCircles() 调用中data 参数是最后一个。

leaflet() %>%
    addProviderTiles(providers$Stamen.Watercolor) %>%
    setView(lng = -79.384293, 
                    lat = 43.685,
                    zoom = 11) %>% 

    addCircles(data = tree_data)

说明

addCircles() 调用中的第一个参数是map，它通过%>% 运算符传入。第二个参数是lng，所以你在调用中所做的相当于

addCircles(lng = tree_data)

另类

将数据发送到addCircles() 函数的另一种方法是通过leaflet() 调用

leaflet(tree_data) %>%
    addProviderTiles(providers$Stamen.Watercolor) %>%
    setView(lng = -79.384293, 
                    lat = 43.685,
                    zoom = 11) %>% 
    addCircles()

【讨论】：

糟糕！感谢您的帮助！