Point clustering - basic configuration

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This sample demonstrates how to enable point clustering on a GeoJSONLayer. Clustering is a method of reducing points in a FeatureLayer, CSVLayer, GeoJSONLayer, or OGCFeatureLayer by grouping them into clusters based on their spatial proximity to one another. Typically, clusters are proportionally sized based on the number of features within each cluster.

Clustering is configured in the featureReduction property of the layer. You can enable clustering with a default configuration with minimal code by setting the type to cluster.

   
layer.featureReduction = {
  type: "cluster"
};

The feature reduction property gives you control over many other cluster properties. The clusterRadius defines area of influence that determines each cluster's region for including features. You may also define popupTemplates and labels for clusters that summarize the features comprised by the cluster.

Configure clustering
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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8" />
  <meta
    name="viewport"
    content="initial-scale=1,maximum-scale=1,user-scalable=no"
  />

    <title>Point clustering - basic configuration | Sample | ArcGIS API for JavaScript 4.19</title>

    <style>
      html,
      body,
      #viewDiv {
        padding: 0;
        margin: 0;
        height: 100%;
        width: 100%;
        background: rgba(50,50,50);
      }
      #infoDiv {
        padding: 10px;
      }
    </style>

    <link rel="stylesheet" href="https://js.arcgis.com/4.19/esri/themes/dark/main.css" />
    <script src="https://js.arcgis.com/4.19/"></script>

    <script>
      require([
        "esri/Map",
        "esri/layers/FeatureLayer",
        "esri/layers/GeoJSONLayer",
        "esri/views/MapView",
        "esri/widgets/Legend",
        "esri/widgets/Expand",
        "esri/widgets/Home"
      ], (Map, FeatureLayer, GeoJSONLayer, MapView, Legend, Expand, Home) => {

        // Configures clustering on the layer. A cluster radius
        // of 100px indicates an area comprising screen space 100px
        // in length from the center of the cluster

        const clusterConfig = {
          type: "cluster",
          clusterRadius: "100px",
          // {cluster_count} is an aggregate field containing
          // the number of features comprised by the cluster
          popupTemplate: {
            title: "Cluster summary",
            content: "This cluster represents {cluster_count} earthquakes.",
            fieldInfos: [{
              fieldName: "cluster_count",
              format: {
                places: 0,
                digitSeparator: true
              }
            }]
          },
          clusterMinSize: "24px",
          clusterMaxSize: "60px",
          labelingInfo: [{
            deconflictionStrategy: "none",
            labelExpressionInfo: {
              expression: "Text($feature.cluster_count, '#,###')"
            },
            symbol: {
              type: "text",
              color: "#004a5d",
              font: {
                weight: "bold",
                family: "Noto Sans",
                size: "12px"
              }
            },
            labelPlacement: "center-center",
          }]
        };


        const layer = new GeoJSONLayer({
          title: "Earthquakes from the last month",
          url: "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_month.geojson",
          copyright: "USGS Earthquakes",

          featureReduction: clusterConfig,

          // popupTemplates can still be viewed on
          // individual features
          popupTemplate: {
            title: "Magnitude {mag} {type}",
            content: "Magnitude {mag} {type} hit {place} on {time}",
            fieldInfos: [
              {
                fieldName: "time",
                format: {
                  dateFormat: "short-date-short-time"
                }
              }
            ]
          },
          renderer: {
            type: "simple",
            field: "mag",
            symbol: {
              type: "simple-marker",
              size: 4,
              color: "#69dcff",
              outline: {
                color: "rgba(0, 139, 174, 0.5)",
                width: 5
              }
            }
          }
        });

        // background layer for geographic context
        // projected to Alaska Polar Stereographic
        const baseLayer = new FeatureLayer({
          portalItem: {
            id: "2b93b06dc0dc4e809d3c8db5cb96ba69"
          },
          legendEnabled: false,
          popupEnabled: false,
          renderer: {
            type: "simple",
            symbol: {
              type: "simple-fill",
              color: [65, 65, 65, 1],
              outline: {
                color: [50, 50, 50, 0.75],
                width: 0.5
              }
            }
          },
          spatialReference: {
            wkid: 5936
          }
        });

        const map = new Map({
          layers: [baseLayer, layer]
        });

        const view = new MapView({
          container: "viewDiv",
          extent: {
            spatialReference: {
              wkid: 5936
            },
            xmin: 1270382,
            ymin: -1729511,
            xmax: 2461436,
            ymax: -953893
          },
          spatialReference: {
            // WGS_1984_EPSG_Alaska_Polar_Stereographic
            wkid: 5936
          },
          constraints: {
            minScale: 15469455
          },
          map: map
        });

        view.ui.add(new Home({
          view: view
        }), "top-left");

        const legend = new Legend({
          view: view,
          container: "legendDiv"
        });

        const infoDiv = document.getElementById("infoDiv");
        view.ui.add(new Expand({
          view: view,
          content: infoDiv,
          expandIconClass: "esri-icon-layer-list",
          expanded: false
        }), "top-left");

        const toggleButton = document.getElementById("cluster");

        // To turn off clustering on a layer, set the
        // featureReduction property to null
        toggleButton.addEventListener("click", () => {
          let fr = layer.featureReduction;
          layer.featureReduction = fr && fr.type === "cluster" ? null : clusterConfig;
          toggleButton.innerText = toggleButton.innerText === "Enable Clustering" ? "Disable Clustering" : "Enable Clustering";
        });
      });
    </script>
  </head>

  <body>
    <div id="viewDiv"></div>
    <div id="infoDiv" class="esri-widget">
      <button id="cluster" class="esri-button">Disable Clustering</button>
      <div id="legendDiv"></div>
    </div>
  </body>
</html>

Suggestions for basic configuration

  • Turn off label deconfliction when labeling clusters with a count in the center of the cluster. If label placement is outside the cluster, keep label deconfliction enabled.
  • Increase the clusterMinSize to fit labels inside smaller clusters (16pt is a good starting point).
  • For larger layers, format the cluster count in the label with either a rounded value or a meaningful abbreviated value (e.g. 10k instead of 10000). See the Point clustering - generate suggested configuration for an example of this.

Point clustering only applies to layers with point geometries in a MapView containing either a SimpleRenderer, UniqueValueRenderer, or a ClassBreaksRenderer. It does not apply to layers with polyline and polygon geometries.

Clustering layers with spatial references other than Web Mercator and WGS-84 is experimental and may not work for every projection. Clustered layers that have spatial references other than Web Mercator or WGS-84 have the same limitations listed in the projection engine documentation.

Click here to read more information about clustering limitations.