Does markercluster work together with leafletProxy() and option iconCreateFunction?

Question

Am I doing something wrong, or why does the below example not work? I am trying to make leaflet markercluster plugin work with leafletProxy() in an R Shiny app, using the option iconCreateFunction. Is the plugin not capable of adding customized icon markers to the map using leafletProxy()?

When I press the first button and zoom out in below example, I get an error saying:

TypeError: this._group.options.iconCreateFunction is not a function

I tried to copy the original example from the markercluster documentation:

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

ui <- fluidPage(
  titlePanel("Hello Shiny!"),
  sidebarLayout(
    sidebarPanel(
      actionButton(inputId = "my_button1",
                   label = "Use leafletProxy()"),
      actionButton(inputId = "my_button2",
                   label = "Use renderLeaflet()")
    ),
    mainPanel(
      leafletOutput(
        outputId = "map",
        width = "100%",
        height = "300px"
      )
    )
  )
)

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

  some_data <- data.frame(
    "lon"=c(4.905167,4.906357,4.905831),
    "lat"=c(52.37712,52.37783,52.37755),
    "number_var"=c(5,9,7),
    "name"=c("Jane","Harold","Mike"),
    stringsAsFactors = F
  )

  output$map <- renderLeaflet({
    return(
      leaflet(data = some_data[0,]) %>%
         addProviderTiles(providers$CartoDB.Positron) %>%
        fitBounds(
          min(some_data$lon),
          min(some_data$lat),
          max(some_data$lon),
          max(some_data$lat)
        ) %>%
        addMarkers(
          lng = ~lon,
          lat = ~lat,
          clusterOptions = markerClusterOptions(
            iconCreateFunction = JS(paste0("function(cluster) {",
                                           "return new L.DivIcon({",
                                           "html: '<div style=\"background-color:rgba(77,77,77,0.5)\"><span>' + cluster.getChildCount() + '</div><span>',",
                                           "className: 'marker-cluster'",
                                           "});",
                                           "}"))



          )
        )
    )
  })

  observeEvent(input$my_button1,{
      leafletProxy(mapId = "map",
                   session = session,
                   data = some_data) %>%
        addProviderTiles(providers$CartoDB.Positron) %>%
        clearMarkerClusters() %>%
        clearMarkers() %>%
        fitBounds(
          min(some_data$lon),
          min(some_data$lat),
          max(some_data$lon),
          max(some_data$lat)
        ) %>%
        addMarkers(
          lng = ~lon,
          lat = ~lat,
          clusterOptions = markerClusterOptions(
            iconCreateFunction = JS(paste0("function(cluster) {",
                                           "console.log('Here comes cluster',cluster); ",
                                           "return new L.DivIcon({",
                                           "html: '<div style=\"background-color:rgba(77,77,77,0.5)\"><span>' + cluster.getChildCount() + '</div><span>',",
                                           "className: 'marker-cluster'",
                                           "});",
                                           "}"))
          )
        )
  })

  observeEvent(input$my_button2,{
    output$map <- renderLeaflet({

      leaflet(data = some_data) %>%
        addProviderTiles(providers$CartoDB.Positron) %>%
        fitBounds(
          min(some_data$lon),
          min(some_data$lat),
          max(some_data$lon),
          max(some_data$lat)
        ) %>%
        addMarkers(
          lng = ~lon,
          lat = ~lat,
          clusterOptions = markerClusterOptions(
            iconCreateFunction = JS(paste0("function(cluster) {",
                                           "console.log('Here comes cluster',cluster); ",
                                           "return new L.DivIcon({",
                                           "html: '<div style=\"background-color:rgba(77,77,77,0.5)\"><span>' + cluster.getChildCount() + '</div><span>',",
                                           "className: 'marker-cluster'",
                                           "});",
                                           "}"))
          )
        )
    })
  })
}

shinyApp(ui = ui, server = server)

Package versions:

dplyr_0.7.4
leaflet_1.1.0
shiny_1.0.5
R version 3.4.3 (2017-11-30)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 16.04.3 LTS

Browser version: Firefox Quantum 57.0.1 (64-bit)

I don't get any errors while running your code. I am on a mac though. — MLavoie
You see markers when pressing both buttons? Thanks for trying. — nilsole
after pressing leafletProxy() the first time yes, but not after with the zoom out — MLavoie
Thanks. That is exactly the problem. The markercluser plugin is supposed to organize the zooming, but in case of leafletProxy this does not seem to work (although dynamically adding markers to the map would be very useful of course). — nilsole
This unanswered question suggests this problem has been around awhile and is referenced in two related github issues (420 and 440) without comment from the team there. — Kevin Arseneau

Kevin Arseneau Kevin Arseneau · Accepted Answer · 2017-12-27T02:04:32

Revised solution

The behaviour of iconCreateFunction is definitely flakey when used within leafletProxy. Although I think there is caching in some browsers making it difficult to track visually.

In order to eliminate the javascript error you were experiencing, it is important to apply layerId and clusterId values as well as using removeMarker in lieu of clearMarkers.

N.B. A strange side-effect of my solution is that a marker is dropped when re-drawn, I'm getting a bit tired and will have another look later. That problem may or may not be trivial.

app.R

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

ui <- fluidPage(
  titlePanel("Hello Shiny!"),
  sidebarLayout(
    sidebarPanel(
      actionButton(inputId = "my_button1",
                   label = "Use leafletProxy()"),
      actionButton(inputId = "my_button2",
                   label = "Use renderLeaflet()")
    ),
    mainPanel(
      leafletOutput(
        outputId = "mymap",
        width = "100%",
        height = "300px"
    ))
))

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

  some_data <- data.frame(
    lon = c(4.905167, 4.906357, 4.905831),
    lat = c(52.37712, 52.37783, 52.37755),
    number_var = c(5, 9, 7),
    name = c("Jane", "Harold", "Mike"),
    stringsAsFactors = FALSE
  )

  marker_js <- JS("function(cluster) {
                  var html = '<div style=\"background-color:rgba(77,77,77,0.5)\"><span>' + cluster.getChildCount() + '</div><span>'
                  return new L.DivIcon({html: html, className: 'marker-cluster'});
                  }")

  output$mymap <- renderLeaflet({

    leaflet(some_data) %>%
      addProviderTiles(providers$CartoDB.Positron) %>%
      fitBounds(
        ~min(lon),
        ~min(lat),
        ~max(lon),
        ~max(lat)
      ) %>%
      addMarkers(
        layerId = "mylayer",
        clusterId = "mycluster",
        lng = ~lon,
        lat = ~lat,
        clusterOptions = markerClusterOptions(
          iconCreateFunction = marker_js
        )
      )

  })

  observeEvent(input$my_button1, {

    leafletProxy("mymap", data = some_data) %>%
      removeMarker(layerId = "mylayer") %>%
      clearTiles %>%
      addProviderTiles(providers$CartoDB.Positron) %>%
      fitBounds(
        ~min(lon),
        ~min(lat),
        ~max(lon),
        ~max(lat)
      ) %>%
      addMarkers(
        layerId = "mylayer",
        clusterId = "mycluster",
        lng = ~lon,
        lat = ~lat,
        clusterOptions = markerClusterOptions(
          iconCreateFunction = marker_js
        )
      )

  })

  observeEvent(input$my_button2,{

    output$mymap <- renderLeaflet({

      leaflet(some_data) %>%
        addProviderTiles(providers$CartoDB.Positron) %>%
        fitBounds(
          ~min(lon),
          ~min(lat),
          ~max(lon),
          ~max(lat)
        ) %>%
        addMarkers(
          layerId = "mylayer",
          clusterId = "mycluster",
          lng = ~lon,
          lat = ~lat,
          clusterOptions = markerClusterOptions(
            iconCreateFunction = marker_js
          )
        )
    })

  })

}

shinyApp(ui = ui, server = server)

in-browser

No other javascript errors were noted.

Does markercluster work together with leafletProxy() and option iconCreateFunction?

2 Answers

Revised solution

app.R

in-browser