如何根据条件面板创建地图？

Question

我正在尝试根据用户选择创建几个传单地图。我尝试制作一个可重现的示例。 我有一个有四种形状的 sf（即代表北卡罗来纳州的四个县）。用户可以根据县的选择来选择绘制一到四个地图（通过“checkboxGroupInput”进行）。如果用户选择一个县，我应该绘制一张代表用户选择的县的地图。如果用户选择两个县，应该绘制两张地图，等等

我有几行代码，但无法将用户选择连接到我的地图。您可以在下面找到我尝试做的事情。

library(sf)
 library(leaflet)
library(mapview)
library(mapedit)
library(DT)
library(viridis)
library(leafem)


nc <- st_read(system.file("shape/nc.shp", package="sf")) %>% head(3)
 
ui = fluidPage(
  titlePanel("Maps"),
  sidebarPanel(
    checkboxGroupInput('MapNumber','Select Maps', choices = c("Ashe", "Alleghany", "Surry"), selected = "Ashe"),
    conditionalPanel(condition="output.MapNum=='1'",
                     fluidRow(
                       column(12,
                              leafletOutput("Map1a")
                       )
                     )
    ),
    conditionalPanel(condition="output.MapNum=='2'",
                     fluidRow(
                       column(6,
                              leafletOutput("Map2a")
                       ),
                       column(6,
                              leafletOutput("Map2b")
                       )
                     )
    ),
    
    conditionalPanel(condition="output.MapNum=='3'",
                     fluidRow(
                       column(6,
                              leafletOutput("Map3a")
                       ),
                       column(6,
                              leafletOutput("Map3b")
                       ),
                       column(6,
                              leafletOutput("Map3c")
                       )
                       
                       )
                     )
    )
    )


server = function(input, output) {
  
  MapInput1a<-reactive({
    req(length(input$MapNumber)==1) 
    input$MapNumber[1] 
  })
  
  MapInput2a<-reactive({
    req(length(input$MapNumber)==2) 
    input$MapNumber[1] 
  })
  
  MapInput2b<-reactive({
    req(length(input$MapNumber)==2) 
    input$MapNumber[2] 
  })  
  
  MapInput3a<-reactive({
    req(length(input$MapNumber)==3) 
    input$MapNumber[1] 
  })  
  
  MapInput3b<-reactive({
    req(length(input$MapNumber)==3) 
    input$MapNumber[2] 
  })  
  
  MapInput3c<-reactive({
    req(length(input$MapNumber)==3) 
    input$MapNumber[3] 
  })  
  
  
  output$Map1a<-renderLeaflet({leaflet()%>% addTiles(group = "OSM") %>%
    addProviderTiles("CartoDB", group = "CartoDB") %>%
    addProviderTiles("Esri.WorldImagery", group = "Esri.WorldImagery") %>%
    addFeatures("?")})# do not know how to plot the feature correctly, and I do not know how to do for output$Map2a, 
 # output$Map2b, etc.
  
}

shinyApp(ui, server)

Answer 1

有趣的问题。我会使用一种相当不同的方法来完成工作。我不会创建那么多条件面板，而是编写一个函数，根据所选县的数量创建列的集合。

library(sf)
library(leaflet)
library(shiny)


nc <- st_read(system.file("shape/nc.shp", package="sf")) %>% head(3)

# This function returns a collection of leaflet plots based on county names
maps_ui <-function(counties, shapefiles) {

  n_counties <- length(counties)
  colum_with <- 12 / n_counties

  maps <- purrr::map(
    counties,
    ~shiny::column(
      width = colum_with,
      leaflet() %>%
        addTiles(group = "OSM") %>%
        addProviderTiles("CartoDB", group = "CartoDB") %>%
        addProviderTiles("Esri.WorldImagery", group = "Esri.WorldImagery") %>%
        addPolygons(data = nc[nc$NAME == .x, ]) %>%
        addLegend(
          position = 'bottomright', 
          colors = c("#5663E2", "#F4BC35", "#E45F71"), 
          labels = c ("1", "2", "3"), 
          opacity = 0.5, title = .x )
    )
      )
  )

  return(maps)

}


# The app

ui = fluidPage(
  checkboxGroupInput('counties', 'Select Maps', choices = c("Ashe", "Alleghany", "Surry"), selected = "Ashe"),
  fluidRow(uiOutput('maps'))
)


server = function(input, output) {

  output$maps <- renderUI({
    maps_ui(input$counties, nc)
  })

}

shinyApp(ui, server)