Add clustering feature reduction to a point feature layer

View inMAUIWinUIWPFView on GitHubSample viewer app

Add client side feature reduction on a point feature layer that is not pre-configured with clustering.

Image of add clustering feature reduction to a point feature layer

Use case

Feature clustering can be used to dynamically aggregate groups of points that are within proximity of each other in order to represent each group with a single symbol. Such grouping allows you to see patterns in the data that are difficult to visualize when a layer contains hundreds or thousands of points that overlap and cover each other. Users can add feature clustering to point feature layers. This is useful when the layer does not have the feature reduction defined or when the existing feature reduction properties need to be overridden.

How to use the sample

Tap the Draw clusters button to set new feature reduction object on the feature layer. Interact with the controls to customize clustering feature reduction properties. Tap on any clustered aggregate geoelement to see the cluster feature count and aggregate fields in the popup.

How it works

  1. Create a map from a web map PortalItem.
  2. Create a ClassBreaksRenderer and define a FieldName and DefaultSymbol. FieldName must be one of the summary fields in the AggregateFields collection.
  3. Add ClassBreak objects each with an associated SimpleMarkerSymbol to the renderer.
  4. Create a ClusteringFeatureReduction using the renderer.
  5. Add AggregateField objects to the feature reduction where the FieldName is the name of the field to aggregate and the StatisticType is the type of aggregation to perform.
  6. Define the MinSymbolSize and MaxSymbolSize for the feature reduction. If these are not defined they default to 12 and 70 respectively.
  7. Add the ClusteringFeatureReduction to the FeatureLayer.
  8. Create a LabelDefinition with a SimpleLabelExpression and TextSymbol to define the cluster label.
  9. Configure a GeoViewTapped event handler on the MapView to display feature cluster information in a PopupViewer.

Relevant API

  • AggregateGeoElement
  • ClassBreaksRenderer
  • FeatureLayer
  • FeatureReduction
  • GeoElement
  • IdentifyLayerResult
  • PopupViewer

About the data

This sample uses a web map that displays residential data for Zurich, Switzerland.

Tags

aggregate, bin, cluster, group, merge, normalize, popup, reduce, renderer, summarize

Sample Code

AddClusteringFeatureReductionToAPointFeatureLayer.xaml.csAddClusteringFeatureReductionToAPointFeatureLayer.xaml.csAddClusteringFeatureReductionToAPointFeatureLayer.xaml
Use dark colors for code blocksCopy
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
// Copyright 2023 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.

using Esri.ArcGISRuntime.ArcGISServices;
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Mapping.Labeling;
using Esri.ArcGISRuntime.Mapping.Popups;
using Esri.ArcGISRuntime.Portal;
using Esri.ArcGISRuntime.Reduction;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.Toolkit.UI.Controls;
using Esri.ArcGISRuntime.UI.Controls;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;

namespace ArcGIS.WPF.Samples.AddClusteringFeatureReductionToAPointFeatureLayer
{
    [ArcGIS.Samples.Shared.Attributes.Sample(
        name: "Add clustering feature reduction to a point feature layer",
        category: "Layers",
        description: "Add client side feature reduction on a point feature layer that is not pre-configured with clustering.",
        instructions: "Tap the `Draw clusters` button to set new feature reduction object on the feature layer. Interact with the controls to customize clustering feature reduction properties. Tap on any clustered aggregate geoelement to see the cluster feature count and aggregate fields in the popup.",
        tags: new[] { "aggregate", "bin", "cluster", "group", "merge", "normalize", "popup", "reduce", "renderer", "summarize" })]
    [ArcGIS.Samples.Shared.Attributes.OfflineData("aa44e79a4836413c89908e1afdace2ea")]
    public partial class AddClusteringFeatureReductionToAPointFeatureLayer
    {
        private FeatureLayer _layer;
        private ClusteringFeatureReduction _clusteringFeatureReduction;

        public AddClusteringFeatureReductionToAPointFeatureLayer()
        {
            InitializeComponent();
            _ = Initialize();
        }

        private async Task Initialize()
        {
            // Get the Zurich buildings web map from the default portal.
            var portal = await ArcGISPortal.CreateAsync();
            PortalItem portalItem = await PortalItem.CreateAsync(portal, "aa44e79a4836413c89908e1afdace2ea");

            // Create a new map from the web map.
            MyMapView.Map = new Map(portalItem);

            // Get the Zurich buildings feature layer once the map has finished loading.
            await MyMapView.Map.LoadAsync();
            _layer = (FeatureLayer)MyMapView.Map.OperationalLayers.First();

            // Set the initial viewpoint to Zurich, Switzerland.
            await MyMapView.SetViewpointAsync(new Viewpoint(47.38, 8.53, 8e4));

            // Enable the draw clusters button after the layer finishes loading.
            await _layer.LoadAsync();
            DrawClustersButton.IsEnabled = true;
        }

        private void CreateCustomFeatureReduction()
        {
            // Create a class breaks renderer to apply to the custom feature reduction.
            ClassBreaksRenderer classBreaksRenderer = new ClassBreaksRenderer();

            // Define the field to use for the class breaks renderer.
            // Note that this field name must match the name of an aggregate field contained in the clustering feature reduction's aggregate fields property.
            classBreaksRenderer.FieldName = "Average Building Height";

            // Add a class break for each intended value range and define a symbol to display for features in that range.
            // In this case, the average building height ranges from 0 to 8 storeys.
            // For each cluster of features with a given average building height, a symbol is defined with a specified color.
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("0", "0", 0.0, 1.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(4, 251, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("1", "1", 1.0, 2.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(44, 211, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("2", "2", 2.0, 3.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(74, 181, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("3", "3", 3.0, 4.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(120, 135, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("4", "4", 4.0, 5.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(165, 90, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("5", "5", 5.0, 6.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(194, 61, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("6", "6", 6.0, 7.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(224, 31, 255) }));
            classBreaksRenderer.ClassBreaks.Add(new ClassBreak("7", "7", 7.0, 8.0, new SimpleMarkerSymbol() { Color = System.Drawing.Color.FromArgb(254, 1, 255) }));

            // Define a default symbol to use for features that do not fall within any of the ranges defined by the class breaks.
            classBreaksRenderer.DefaultSymbol = new SimpleMarkerSymbol() { Color = System.Drawing.Color.Pink };

            // Create a new clustering feature reduction using the class breaks renderer.
            _clusteringFeatureReduction = new ClusteringFeatureReduction(classBreaksRenderer);

            // Set the feature reduction's aggregate fields. Note that the field names must match the names of fields in the feature layer's dataset.
            // The aggregate fields summarize values based on the defined aggregate statistic type.
            _clusteringFeatureReduction.AggregateFields.Add(new AggregateField("Total Residential Buildings", "Residential_Buildings", AggregateStatisticType.Sum));
            _clusteringFeatureReduction.AggregateFields.Add(new AggregateField("Average Building Height", "Most_common_number_of_storeys", AggregateStatisticType.Mode));

            // Enable the feature reduction.
            _clusteringFeatureReduction.IsEnabled = true;

            // Set the popup definition for the custom feature reduction.
            _clusteringFeatureReduction.PopupDefinition = PopupDefinition.FromPopupSource(_clusteringFeatureReduction);

            // Set values for the feature reduction's cluster minimum and maximum symbol sizes.
            // Note that the default values for Max and Min symbol size are 70 and 12 respectively.
            _clusteringFeatureReduction.MinSymbolSize = 5;
            _clusteringFeatureReduction.MaxSymbolSize = 90;

            // Set the feature reduction for the layer.
            _layer.FeatureReduction = _clusteringFeatureReduction;

            // Populate the cluster radius and max scale pickers with default values.
            ClusterRadiusPicker.ItemsSource = new double[] { 30, 45, 60, 75, 90 };
            MaxScalePicker.ItemsSource = new double[] { 0, 1000, 5000, 10000, 50000, 100000, 500000 };

            // Set initial picker values.
            // Note that the default value for cluster radius is 60.
            // Increasing the cluster radius increases the number of features that are grouped together into a cluster.
            ClusterRadiusPicker.SelectedValue = _clusteringFeatureReduction.Radius;

            // Note that the default value for max scale is 0.
            // The max scale value is the maximum scale at which clustering is applied.
            MaxScalePicker.SelectedValue = _clusteringFeatureReduction.MaxScale;
        }

        #region EventHandlers

        private void DisplayLabelsCheckBox_Checked(object sender, RoutedEventArgs e)
        {
            if ((bool)(sender as CheckBox).IsChecked)
            {
                // Create a label definition with a simple label expression.
                var simpleLabelExpression = new SimpleLabelExpression("[cluster_count]");
                var textSymbol = new TextSymbol() { Color = System.Drawing.Color.Black, Size = 15d, FontWeight = Esri.ArcGISRuntime.Symbology.FontWeight.Bold };
                var labelDefinition = new LabelDefinition(simpleLabelExpression, textSymbol) { Placement = LabelingPlacement.PointCenterCenter };

                // Add the label definition to the feature reduction.
                _clusteringFeatureReduction.LabelDefinitions.Add(labelDefinition);
            }
            else
            {
                _clusteringFeatureReduction.LabelDefinitions.Clear();
            }
        }

        // When a new picker item is selected, update the feature reduction cluster radius.
        private void ClusterRadiusPicker_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (_layer != null)
            {
                ((ClusteringFeatureReduction)_layer.FeatureReduction).Radius = (double)ClusterRadiusPicker.SelectedItem;
            }
        }

        // When a new picker item is selected, update the feature reduction max scale.
        private void MaxScalePicker_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (_layer != null)
            {
                ((ClusteringFeatureReduction)_layer.FeatureReduction).MaxScale = (double)MaxScalePicker.SelectedValue;
            }
        }

        private async void MyMapView_GeoViewTapped(object sender, GeoViewInputEventArgs e)
        {
            // Identify the tapped observation.
            IdentifyLayerResult result = await MyMapView.IdentifyLayerAsync(MyMapView.Map.OperationalLayers.First(), e.Position, 3, true);

            // Return if no observations were found.
            if (result.Popups.Count == 0) return;

            // Set the popup and make it visible.
            PopupViewer.Popup = result.Popups.FirstOrDefault();
            PopupBackground.Visibility = Visibility.Visible;
        }

        private void DrawClustersButton_Clicked(object sender, RoutedEventArgs e)
        {
            // Create a new clustering feature reduction.
            CreateCustomFeatureReduction();

            // Show the feature reduction's clustering options.
            ClusteringOptions.Visibility = Visibility.Visible;

            // Add an event handler for tap events on the map view.
            MyMapView.GeoViewTapped += MyMapView_GeoViewTapped;

            // Hide the draw clusters button.
            DrawClustersButton.Visibility = Visibility.Collapsed;
        }

        // Hide and nullify the opened popup when user left clicks.
        private void PopupBackground_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            PopupBackground.Visibility = Visibility.Collapsed;
            PopupViewer.Popup = null;
        }

        #endregion EventHandlers
    }
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.