R Shiny Leaflet Show number of overlapping markers / polygons?

Question

I'm working with a large set of location data, and it turns out a lot of my locations share longitude and latitude values. Is there a way to show the number of markers / polygons that overlap, either through a popup or some other widget?

I can not remove sites that share longitude and latitude values from my dataset.

#############################################
# Needed Libraries & Input Files

library(shiny)
library(shinydashboard)
library(leaflet)

## The Data
Point_ID = c("A1", "B1", "C1")
Latitude = c(38.00, 38.00, 38.00)
Longitude = c(-107.00, -107.00, -107.00)
Map_DF <- data.frame(Point_ID, Latitude, Longitude)

choiseList <- c("A1", "B1", "C1")

#############################################
# UI
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(checkboxGroupInput(inputId = "IDPointInput", label = "Select Point ID", choices = choiseList, selected = choiseList)),
  dashboardBody(fluidRow(leafletOutput(outputId = 'mapA')))
)

#############################################
# SERVER
server <- function(input, output, session) {
  
  ## The Filter
  filter_df <- reactive({
    Map_DF[sapply(Map_DF$Point_ID, function(p) {any(input$IDPointInput %in% p)}), ]
  })
  
  ## Base Map Creation
  output$mapA <- renderLeaflet({
    leaflet() %>%
      addProviderTiles(
        providers$Esri.DeLorme,
        options = providerTileOptions(
          updateWhenZooming = FALSE,
          updateWhenIdle = TRUE)
      ) %>%
      setView(lng = -107.50, lat = 39.00, zoom = 7)
  })
  
  ## Update Map with Filter Selection
  observe({
    leafletProxy("mapA", session) %>%
      clearMarkers() %>%
      addCircleMarkers(
        data = filter_df(),
        radius = 10,
        color = "red",
        lat = ~Latitude,
        lng = ~Longitude,
        popupOptions(autoPan = FALSE),
        popup = ~paste("PointID: ", filter_df()$Point_ID))
        # Show number of sites that overlap oneanother
  })
}

############################################
shinyApp(ui = ui, server = server)

Answer 1

Does addAwesomeMarkers work for you?

library(shiny)
library(shinydashboard)
library(leaflet)

## The Data
Point_ID = c("A1", "B1", "C1")
Latitude = c(38.00, 38.00, 38.00)
Longitude = c(-107.00, -107.00, -107.00)
Map_DF <- data.frame(Point_ID, Latitude, Longitude)

choiseList <- c("A1", "B1", "C1")

#############################################
# UI
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(checkboxGroupInput(inputId = "IDPointInput", label = "Select Point ID", choices = choiseList, selected = choiseList)),
  dashboardBody(fluidRow(leafletOutput(outputId = 'mapA')))
)

#############################################
# SERVER
server <- function(input, output, session) {
  
  ## The Filter
  filter_df <- reactive({
    Map_DF[sapply(Map_DF$Point_ID, function(p) {any(input$IDPointInput %in% p)}), ]
  })
  
  ## Base Map Creation
  output$mapA <- renderLeaflet({
    leaflet(filter_df()) %>% 

      addProviderTiles(
        providers$Esri.DeLorme,
        options = providerTileOptions(
          updateWhenZooming = FALSE,
          updateWhenIdle = TRUE)
      )  %>%
      
      setView(lng = -107.50, lat = 39.00, zoom = 7) %>% 
      
     # use addAwesomeMarkers #
      addAwesomeMarkers(
        lat = ~Latitude,
        lng = ~Longitude,
        icon=~makeAwesomeIcon(
          icon = 'ios-close',
          iconColor = 'black',
          library = 'ion',
          markerColor = 'orange'),
        
        label=~as.character(Point_ID),
        
        popup = ~paste("PointID: ", Point_ID),
        
        clusterOptions = markerClusterOptions()
      )
  })
}

############################################
shinyApp(ui = ui, server = server)