Leaflet/shiny: 无法绘制反应多边形

Question

查看 Shiny integration example on the Leaflet for R page 后，我在设置子集和显示一些要在我闪亮的应用程序中显示的多边形时遇到问题。

目前，我正在安装一个带有侧边栏的应用程序，但主显示屏只是 "Error:Don't know how to get path data from object of class reactive"

想法是从 GB（3 个国家/地区）中选择一个国家/地区多边形并根据下拉选项单独显示它；

require(shiny)
require(rgdal)
require(rgeos)
require(leaflet)

cont <- readOGR(".\mypath\mypolygons.shp", "mypolygons", stringsAsFactors=FALSE)

ui <- fluidPage(

  titlePanel("My page"),

  sidebarLayout(
    sidebarPanel(
      selectInput("countryInput", "Country:", choices = c('England','Scotland','Wales'))
    ),
    mainPanel(
      leafletOutput("mymap")
    )
  )
)

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

pols <- eventReactive(input$countryInput,{cont[substr(cont@data$code,1,1)==substr(input$countryInput,1,1),]})

  output$mymap <- renderLeaflet({
    leaflet() %>%
      addProviderTiles("CartoDB.Positron") %>%
      addPolygons(data = pols)
  })
}


shinyApp(ui, server)

错误：

Warning: Error in polygonData.default: Don't know how to get path data from object of class reactive
Stack trace (innermost first):
    83: polygonData.default
    82: polygonData
    81: derivePolygons
    80: addPolygons
    79: function_list[[k]]
    78: withVisible
    77: freduce
    76: _fseq
    75: eval
    74: eval
    73: withVisible
    72: %>%
    71: func [#6]
    70: output$mymap
     4: <Anonymous>
     3: do.call
     2: print.shiny.appobj
     1: <Promise>

Answer 1

修复：

首先我改变了；

pols <- eventReactive(input$countryInput,{cont[substr(cont@data$code,1,1)==substr(input$countryInput,1,1),]})

到；

pols <- reactive({cont.sim[substr(cont.sim@data$gssCode,1,1)==substr(input$countryInput,1,1),]

并且 'addPolygons 行在变量名 'pols'

后缺少 open/close 方括号

addPolygons(data = pols)

变成

addPolygons(data = pols())

Leaflet/shiny: 无法绘制反应多边形

Leaflet/shiny: cannot draw reactive polygons

r

polygon

leaflet

shiny