如何仅在超过阈值时更新?

在下面的代码中,在缩放更改后,将绘制两次传单添加圆。我认为出现这种双重绘图是因为反应式绘图需要创建数据帧 随着缩放的更改而更新。然而,我只想在超过缩放阈值时更新被动数据帧(race.dots.all.r)。有什么想法吗?

编辑:为了简化,我删除了更多的代码,并通过在数据中添加dropbox链接使其可复制。

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

load(url("https://www.dropbox.com/s/umhqvoqvbhlkrc6/shiny_app_seg_gap_stackoverflow.RData?dl=1"))

ui <- shinyUI(fluidPage(
  leafletOutput("map"),
  checkboxInput("togglewhite",  "White", value = TRUE)
                            ))


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

  per.person <- eventReactive(input$map_zoom,{

    new_zoom <- 12
    if (!is.null(input$map_zoom)) {
      new_zoom <- input$map_zoom}

    if ( new_zoom < 13 ) {
      per.person <- "1000"
    } else {
      per.person <- "250"
    }

    return(per.person)

  })

  race.dots.all.r <- eventReactive(per.person(),{
    race.dots.all <- race.dots.all[[per.person()]]
    return(race.dots.all)
  })


  values <- reactiveValues(school = NULL)

  output$map <- renderLeaflet({

    leaflet(options = leafletOptions(preferCanvas = TRUE)) %>% 
      addProviderTiles("CartoDB") %>%
      setView(lat=40.73771, lng=-74.18958, zoom = 8)
  })


  observeEvent(c(input$togglewhite, race.dots.all.r()), {

    proxy <- leafletProxy('map')
    proxy %>% clearGroup(group = "White")
    if (input$togglewhite){
      race.dots.all.selected.race <- dplyr::filter( race.dots.all.r(), group == "White")
      proxy %>% addCircles(group = race.dots.all.selected.race$group, 
                           race.dots.all.selected.race$lng, 
                           race.dots.all.selected.race$lat)
    }
  },ignoreInit = TRUE)

}) # close server

shinyApp(ui, server)