clustermarkers in leaflet providing density information in R

Question

I am wondering if it is possible for clusterMarkers in leaflet to display frequency information instead of the number of markers clustered?

I have the following code

getColor <- function(my.df) {
  sapply(my.df$value, function(value) {
  if(value <= 5) {
    "green"
  } else if(value <= 25) {
    "orange"
  } else {
    "red"
  } })
}
icons <- awesomeIcons(
  icon = 'ios-close',
  iconColor = 'black',
  library = 'ion',
  markerColor = getColor(my.df)
)


map <- my.df %>% 
    leaflet () %>%
    addTiles() %>%
    addAwesomeMarkers(icon=icons, label=~as.character(freq), clusterOptions = markerClusterOptions())
map

my.df is in the following format

longitude latitude freq
XX.xxx    XX.xxx    3
XX.xxx    XX.xxx    7
XX.xxx    XX.xxx    4
.
.
.
XX.xxx    XX.xxx    6

What I would like is for the cluster to display the aggregate of the value for my.df$freq rather than the number of pins in the cluster. I am not sure how to do this though or if there is even a clusterOption for this.

please report `dput(my.df)`. https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example — Iman, Aug 05 '18 at 15:19

score 3 · Answer 1 · answered Jul 11 '18 at 12:41

Yes, this is possible.

You have to make use of iconCreateFunction function which is inserted as an option to MarkerClusterGroup for creating custom cluster icons. You also need to make use of getAllChildMarkers() function to iterate through all children of a cluster and calculate aggregate value.

var markers = L.markerClusterGroup({
    iconCreateFunction: function(cluster) {
        let children = cluster.getAllChildMarkers();

        let sum = 0;
        for (let i = 0; i < children.length; i++) {
            sum += children[i].options.value;
        }

        return new L.DivIcon({ html: '<b>' + sum + '</b>' });
    }
}).addTo(map);

L.circleMarker([0,0], {value: 10}).addTo(markers);
L.circleMarker([10,0], {value: 20}).addTo(markers);
L.circleMarker([40,10], {value: 60}).addTo(markers);

Of course, you can customize the icon.

This jsfiddle: https://jsfiddle.net/41mknp5s/1/ is an implementation of the above code. Zoom in/out to see the cluster showing the sum values of the markers.

I am unable to implement this correctly in R. Do you have any suggestions? — JWH2006, Jul 12 '18 at 12:50
I don't know R but I would suggest you share your code with us. — treecon, Jul 13 '18 at 08:50
As I mentioned, I dont know R but I wrote the logic in Javascript, for a plugin that is written in Javascript. You could transform it to R code. — treecon, Aug 01 '18 at 11:54

clustermarkers in leaflet providing density information in R

1 Answers1