拆分一张传单图的代码（这样一部分的输入更新不会影响另一部分代码）

Question

是否可以拆分地图的代码，以便地图的一部分仅在其自身的输入发生更改时更新？

在下面的可重现示例中，当 select 使用“墨粉”图块并 select 使用新站时，整个传单地图将再次执行，因为 addLegend 需要更新。这使得磁贴跳回“OSM（默认）”磁贴。当我 select 其他车站时，我想留在我 select 的瓷砖。

library(leaflet)
library(shiny)
library(dplyr)

pal <- colorFactor(
  palette = "YlGnBu",
  domain = quakes$stations
)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      checkboxGroupInput("stations", 
                  "Choose a station",
                  choices=sort(unique(quakes$stations)),
                  selected = c(10, 11))
    ),
    mainPanel(
      leafletOutput("map")
    )
  )
)

server <- function(input, output) {
  points <- reactive({
    quakes %>%
      filter(stations %in% input$stations)
  })
  
  output$map <- renderLeaflet({
    leaflet(quakes) %>%
      addTiles(group = "OSM (default)") %>%
      addProviderTiles(providers$Stamen.Toner, group = "Toner") %>%
      addLayersControl(
        baseGroups = c("OSM (default)", "Toner"),
        options = layersControlOptions(collapsed = FALSE)) %>%
      addLegend("Legend", position = "topleft", pal = pal, values = input$stations)
  })
  
  observe({
    if(nrow(points()) == 0) {
      leafletProxy("map", data = points()) %>%
        clearMarkers()
    } else {
      leafletProxy("map", data = points()) %>%
        clearMarkers() %>%
        addCircleMarkers(radius = 2)
    }
  })
}

shinyApp(ui, server)

我尝试了几种方法，包括将 addLegend 添加到 else 语句中，但效果并不理想。我是 leaflet/shiny 的新手，移动 addLegend 对我来说似乎最合乎逻辑。我非常感谢任何建议！

Answer 1

据我所知，您尝试将 addLegend 移动到观察者处是在正确的轨道上。这样做对我来说很好。

将 addLegend 移动到 observe
在添加图例之前，请使用 clearControls 删除任何现有图例（否则您会得到多个图例）
我删除了 observe
据我所知，条件 nrow(points()) > 0 只需要决定是否应该绘制图例。对于标记没关系。


    library(leaflet)
    library(shiny)
    library(dplyr)
    
    pal <- colorFactor(
      palette = "YlGnBu",
      domain = quakes$stations
    )
    
    ui <- fluidPage(
      sidebarLayout(
        sidebarPanel(
          checkboxGroupInput("stations", 
                             "Choose a station",
                             choices=sort(unique(quakes$stations)),
                             selected = c(10, 11))
        ),
        mainPanel(
          leafletOutput("map")
        )
      )
    )
    
    server <- function(input, output) {
      points <- reactive({
        quakes %>%
          filter(stations %in% input$stations)
      })
      
      output$map <- renderLeaflet({
        leaflet(quakes) %>%
          addTiles(group = "OSM (default)") %>%
          addProviderTiles(providers$Stamen.Toner, group = "Toner") %>%
          addLayersControl(
            baseGroups = c("OSM (default)", "Toner"),
            options = layersControlOptions(collapsed = FALSE))
      })
      
      observe({
        proxy <- leafletProxy("map", data = points()) %>%
          clearMarkers() %>% 
          clearControls() %>% 
          addCircleMarkers(radius = 2)
        
        if (nrow(points()) > 0) 
          proxy <- proxy %>% addLegend("Legend", position = "topleft", pal = pal, values = input$stations)
        
        proxy
      })
    
    }
    
    shinyApp(ui, server)

拆分一张传单图的代码（这样一部分的输入更新不会影响另一部分代码）

Split code of one leaflet map (so that input updates of one part does not affect other part of code)

r

leaflet

shiny

shinydashboard