基于缩放级别的闪亮传单显示标签

问题描述

我想基于缩放级别显示我的标记标签.基于( https://rstudio.github.io/leaflet/shiny.html )我尝试使用"input $ MAPID_zoom".在我的示例中，当缩放级别(mapscale)低于6时，应显示存储在location_name中的标签.

I want to display my marker labels based on zoom level.Based on (https://rstudio.github.io/leaflet/shiny.html) I tried to use "input$MAPID_zoom". In my example, labels stored in location_name should be displayed when zoom level (mapscale) is lower to 6.

我尝试过的:

library(shiny)
library(leaflet)

 # my data
df <- data.frame(
  location_name = c('S1', 'S2'),
  lng = c(-1.554136,  -2.10401),
  lat = c(47.218637, 47.218637),
  stringsAsFactors = FALSE)


# UI
 ui <- shinyUI(fluidPage(
  leafletOutput('map')

  ))

# server

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

  mapscale <-  observe({
    input$map_zoom   # get zoom level
  })


  output$map <- renderLeaflet({
    leaflet() %>%
    addTiles() %>%
    addMarkers(data=df, lng = ~lng, lat = ~lat,
               label =~if(mapscale<6, location_name))
})

})

shinyApp(ui = ui, server = server)

推荐答案

如果您愿意，可以在代码中添加一些说明.如果将缩放包装为反应式功能，请像mapscale()一样引用它.在R中使用普通的if语句，在变量前使用~.那你应该没事的.

A few remarks on your code if you like.If you wrap the zoom in a reactive function, reference it like mapscale(). Use the normal if statement in R and the ~ in front of the variable. Then you should be fine.

可复制的示例:

library(shiny)
library(leaflet)

df <- data.frame(
  location_name = c('S1', 'S2'),
  lng = c(-1.554136,  -2.10401),
  lat = c(47.218637, 47.218637),
  stringsAsFactors = FALSE
)


ui <- shinyUI(
  fluidPage(
    leafletOutput(outputId = 'map')
  )
)

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

  output$map <- renderLeaflet({
    leaflet() %>%
      addTiles()
  })

  observeEvent(
    eventExpr = input$map_zoom, {
      print(input$map_zoom)           # Display zoom level in the console
      leafletProxy(
        mapId = "map",
        session = session
      ) %>%
        clearMarkers() %>%
        addMarkers(
          data = df,
          lng = ~lng,
          lat = ~lat,
          label = if(input$map_zoom < 6) ~location_name
      )
    }
  )


})

shinyApp(
  ui = ui,
  server = server
)

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