Point clustering with visual variables

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This sample demonstrates how point clustering can be used to group points into clusters based on their spatial proximity to one another. Clustering is enabled on the layer's featureReduction property.

Since featureReduction is independent of the renderer, the symbol and popupTemplate of each cluster graphic can be used to summarize features within the cluster. See Clustering styles and configurations for more information about the various ways clusters can summarize the points they represent.

The layer's renderer in this sample visualizes weather data with three visual variables, each representing a different attribute:

  • Color: TEMP
  • Size: WIND_SPEED
  • Rotation: WIND_DIRECT

The renderer object looks like the the following:

Calculate cluster statistics
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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 with visual variables | Sample | ArcGIS API for JavaScript 4.19</title>

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


  <style>
    html, body, #viewDiv {
      height: 100%;
      width: 100%;
      margin: 0;
      padding: 0;
      background-color: white;
    }
    #infoDiv {
      background: white;
      padding: 10px;
    }
  </style>


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

      // Displays each weather station with three variables:
      // Rotation - indicates wind direction
      // Color - indicates air temperature
      // Size - indicates wind speed


      const renderer = {
        type: "simple", // autocasts as new SimpleRenderer()
        symbol: {
          type: "simple-marker", // autocasts as new SimpleMarkerSymbol()
          // Arrow marker
          path: "M14.5,29 23.5,0 14.5,9 5.5,0z",
          color: [50, 50, 50],
          outline: {
            color: [0, 0, 0, 0.7],
            width: 0.5
          },
          angle: 180,
          size: 15
        },
        visualVariables: [
          {
            type: "rotation",
            // Use {cluster_avg_WIND_DIRECT} in the
            // featureReudction.popupTemplate to
            // display the average temperature of all
            // features within the cluster
            field: "WIND_DIRECT",
            rotationType: "geographic"
          },
          {
            type: "size",
            // Use {cluster_avg_WIND_SPEED} in the
            // featureReudction.popupTemplate to
            // display the average temperature of all
            // features within the cluster
            field: "WIND_SPEED",
            minDataValue: 0,
            maxDataValue: 60,
            minSize: 8,
            maxSize: 40
          },
          {
            type: "color",
            // Use {cluster_avg_TEMP} in the
            // featureReudction.popupTemplate to
            // display the average temperature of all
            // features within the cluster
            field: "TEMP",
            stops: [
              { value: 20, color: "#2b83ba" },
              { value: 35, color: "#abdda4" },
              { value: 50, color: "#ffffbf" },
              { value: 65, color: "#fdae61" },
              { value: 80, color: "#d7191c" }
            ]
          }
        ]
      };


      // Configures clustering on the layer including
      // a popupTemplate referring to aggregate fields
      // that summarize the values of the fields used
      // to render the cluster graphics.


      const clusterConfig = {
        type: "cluster",
        popupTemplate: {
          content: [{
            type: "text",
            text: "This cluster represents <b>{cluster_count}</b> weather stations."
          }, {
            type: "fields",
            fieldInfos: [{
              fieldName: "cluster_avg_WIND_SPEED",
              label: "Average wind speed (km/h)",
              format: {
                places: 0
              }
            }, {
              fieldName: "cluster_avg_WIND_DIRECT",
              label: "Average wind direction (degrees)",
              format: {
                places: 0
              }
            }, {
              fieldName: "cluster_avg_TEMP",
              label: "Average temperature (°F)",
              format: {
                places: 0
              }
            }]
          }]
        }
      };


      const layer = new FeatureLayer({
        portalItem: {
          id: "cb1886ff0a9d4156ba4d2fadd7e8a139"
        },
        renderer,
        featureReduction: clusterConfig
      });

      // Layer used only for geographic context

      const baseLayer = new FeatureLayer({
        portalItem: {
          id: "2b93b06dc0dc4e809d3c8db5cb96ba69"
        },
        legendEnabled: false,
        popupEnabled: false,
        renderer: {
          type: "simple",
          symbol: {
            type: "simple-fill",
            color: [200, 200, 200, 0.75],
            outline: {
              color: "white",
              width: 0.5
            }
          }
        }
      });

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


      const spatialReference = {
        wkid: 54036
      };

      const view = new MapView({
        container: "viewDiv",
        map,
        center: {
          x: 0,
          y: 0,
          spatialReference: spatialReference
        },
        spatialReference: spatialReference,
        scale: 100000000,
        constraints: {
          rotationEnabled: false
        },
        graphics: [
          {
            symbol: {
              type: "simple-fill",
              color: null,
              outline: {
                width: 1,
                color: [200, 200, 200, 0.75]
              }
            },
            geometry: {
              type: "extent",
              xmin: -180,
              xmax: 180,
              ymin: -90,
              ymax: 90,
              spatialReference: { wkid: 4326 }
            }
          }
        ]
      });

      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: true
      }), "top-right");

      const toggleButton = document.getElementById("toggle-cluster");
      toggleButton.addEventListener("click", toggleClustering);

      // To turn off clustering on a layer, set the
      // featureReduction property to null
      function toggleClustering () {
        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="toggle-cluster" class="esri-button">Disable Clustering</button>
      <div id="legendDiv"></div>
    </div>
  </body>

  </html>

To enable clustering on the layer, you simply have to set the featureReduction property to type cluster,

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

This will cluster the points using the default clusterRadius (80px), and assign a symbol to each cluster conforming to the visualVariables in the renderer in the following manner:

  • Color: average TEMP of all features in the cluster
  • Size: average WIND_SPEED of all features in the cluster
  • Rotation: average WIND_DIRECT of all features in the cluster
No feature reductionClustered features
clustering-color-size-disabled clustering-color-size-enabled )

If a UniqueValueRenderer were used, the symbol of the predominant uniqueValueInfo among the features in the cluster would be used to represent the cluster.

To provide more meaning to the app, you can configure a popupTemplate to display the average values of all the fields used by the renderer when the user clicks or taps the cluster.

Configure clustering based on renderer
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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 with visual variables | Sample | ArcGIS API for JavaScript 4.19</title>

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


  <style>
    html, body, #viewDiv {
      height: 100%;
      width: 100%;
      margin: 0;
      padding: 0;
      background-color: white;
    }
    #infoDiv {
      background: white;
      padding: 10px;
    }
  </style>


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

      // Displays each weather station with three variables:
      // Rotation - indicates wind direction
      // Color - indicates air temperature
      // Size - indicates wind speed


      const renderer = {
        type: "simple", // autocasts as new SimpleRenderer()
        symbol: {
          type: "simple-marker", // autocasts as new SimpleMarkerSymbol()
          // Arrow marker
          path: "M14.5,29 23.5,0 14.5,9 5.5,0z",
          color: [50, 50, 50],
          outline: {
            color: [0, 0, 0, 0.7],
            width: 0.5
          },
          angle: 180,
          size: 15
        },
        visualVariables: [
          {
            type: "rotation",
            // Use {cluster_avg_WIND_DIRECT} in the
            // featureReudction.popupTemplate to
            // display the average temperature of all
            // features within the cluster
            field: "WIND_DIRECT",
            rotationType: "geographic"
          },
          {
            type: "size",
            // Use {cluster_avg_WIND_SPEED} in the
            // featureReudction.popupTemplate to
            // display the average temperature of all
            // features within the cluster
            field: "WIND_SPEED",
            minDataValue: 0,
            maxDataValue: 60,
            minSize: 8,
            maxSize: 40
          },
          {
            type: "color",
            // Use {cluster_avg_TEMP} in the
            // featureReudction.popupTemplate to
            // display the average temperature of all
            // features within the cluster
            field: "TEMP",
            stops: [
              { value: 20, color: "#2b83ba" },
              { value: 35, color: "#abdda4" },
              { value: 50, color: "#ffffbf" },
              { value: 65, color: "#fdae61" },
              { value: 80, color: "#d7191c" }
            ]
          }
        ]
      };


      // Configures clustering on the layer including
      // a popupTemplate referring to aggregate fields
      // that summarize the values of the fields used
      // to render the cluster graphics.


      const clusterConfig = {
        type: "cluster",
        popupTemplate: {
          content: [{
            type: "text",
            text: "This cluster represents <b>{cluster_count}</b> weather stations."
          }, {
            type: "fields",
            fieldInfos: [{
              fieldName: "cluster_avg_WIND_SPEED",
              label: "Average wind speed (km/h)",
              format: {
                places: 0
              }
            }, {
              fieldName: "cluster_avg_WIND_DIRECT",
              label: "Average wind direction (degrees)",
              format: {
                places: 0
              }
            }, {
              fieldName: "cluster_avg_TEMP",
              label: "Average temperature (°F)",
              format: {
                places: 0
              }
            }]
          }]
        }
      };


      const layer = new FeatureLayer({
        portalItem: {
          id: "cb1886ff0a9d4156ba4d2fadd7e8a139"
        },
        renderer,
        featureReduction: clusterConfig
      });

      // Layer used only for geographic context

      const baseLayer = new FeatureLayer({
        portalItem: {
          id: "2b93b06dc0dc4e809d3c8db5cb96ba69"
        },
        legendEnabled: false,
        popupEnabled: false,
        renderer: {
          type: "simple",
          symbol: {
            type: "simple-fill",
            color: [200, 200, 200, 0.75],
            outline: {
              color: "white",
              width: 0.5
            }
          }
        }
      });

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


      const spatialReference = {
        wkid: 54036
      };

      const view = new MapView({
        container: "viewDiv",
        map,
        center: {
          x: 0,
          y: 0,
          spatialReference: spatialReference
        },
        spatialReference: spatialReference,
        scale: 100000000,
        constraints: {
          rotationEnabled: false
        },
        graphics: [
          {
            symbol: {
              type: "simple-fill",
              color: null,
              outline: {
                width: 1,
                color: [200, 200, 200, 0.75]
              }
            },
            geometry: {
              type: "extent",
              xmin: -180,
              xmax: 180,
              ymin: -90,
              ymax: 90,
              spatialReference: { wkid: 4326 }
            }
          }
        ]
      });

      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: true
      }), "top-right");

      const toggleButton = document.getElementById("toggle-cluster");
      toggleButton.addEventListener("click", toggleClustering);

      // To turn off clustering on a layer, set the
      // featureReduction property to null
      function toggleClustering () {
        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="toggle-cluster" class="esri-button">Disable Clustering</button>
      <div id="legendDiv"></div>
    </div>
  </body>

  </html>

clustering-color-size-popup

Enabling clustering on 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.