【R】Shinyとleafletで地図上の座標取得

library(shiny)
library(leaflet)
library(htmlwidgets)
ui <- fluidPage(
  leafletOutput("map"),
  br(),
  verbatimTextOutput("out"),
  verbatimTextOutput("out2")
  
  
)
server <- function(input, output, session) {
  output$map <- renderLeaflet({
    leaflet()  %>%
      addProviderTiles("OpenStreetMap.Mapnik") %>%
      setView(135,35, zoom = 7) %>%
      onRender(
        "function(el,x){
                    this.on('mousemove', function(e) {
                        var lat = e.latlng.lat;
                        var lng = e.latlng.lng;
                        var coord = [lat, lng];
                        Shiny.onInputChange('hover_coordinates', coord)
                    });
                    this.on('mouseout', function(e) {
                        Shiny.onInputChange('hover_coordinates', null)
                    })
                }"
      )
    
  })
  
  output$out <- renderText({
    if(is.null(input$hover_coordinates)) {
      "Mouse outside of map"
    } else {
      paste0("Lat: ", input$hover_coordinates[1], 
             "\nLng: ", input$hover_coordinates[2])
    }
  })
  
  ## Observe mouse clicks and add circles
  observeEvent(input$map_click, {
    click <- input$map_click
    clat <- click$lat
    clng <- click$lng
    output$out2 <- renderText({
          validate(need(input$map_click, FALSE))
          paste0("Lat: ", clat, 
                 "\nLng: ", clng)
    })
    
    leafletProxy('map') %>%
      addCircles(lng=clng, lat=clat, group='circles',
                 weight=1, radius=300, color='black', fillColor='green',
                 fillOpacity=0.2, opacity=1)
  })  
  
}
shinyApp(ui, server)