Statistical query

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Query a table to get aggregated statistics back for a specific field.

Image of statistical query

Use case

For example, a county boundaries table with population information can be queried to return aggregated results for total, average, maximum, and minimum population, rather than downloading the values for every county and calculating statistics manually.

How to use the sample

Pan and zoom to define the extent for the query. Use the 'Only cities in current extent' checkbox to control whether the query only includes features in the visible extent. Use the 'Only cities greater than 5M' checkbox to filter the results to only those cities with a population greater than 5 million people. Click 'Get statistics' to perform the query. The query will return population-based statistics from the combined results of all features matching the query criteria.

How it works

  1. Create a ServiceFeatureTable with a URL to the feature service.
  2. Create StatisticsQueryParameters, and StatisticDefinition objects, and add to the parameters.
  3. Execute queryStatistics() on the ServiceFeatureTable. Depending on the state of the two checkboxes, additional parameters are set.
  4. Display each StatisticRecord in the first returned QueryStatisticsResult.

Relevant API

  • QueryParameters
  • ServiceFeatureTable
  • StatisticDefinition
  • StatisticRecord
  • StatisticsQueryParameters
  • StatisticsQueryResult
  • StatisticType

Tags

analysis, average, bounding geometry, filter, intersect, maximum, mean, minimum, query, spatial query, standard deviation, statistics, sum, variance

Sample Code

StatisticalQuerySample.java
                                                                                                                                                                                           
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/*
 * Copyright 2018 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.
 */

package com.esri.samples.statistical_query;

import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.CheckBox;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.layout.CornerRadii;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Paint;
import javafx.stage.Stage;

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.concurrent.ListenableFuture;
import com.esri.arcgisruntime.data.QueryParameters;
import com.esri.arcgisruntime.data.ServiceFeatureTable;
import com.esri.arcgisruntime.data.StatisticDefinition;
import com.esri.arcgisruntime.data.StatisticRecord;
import com.esri.arcgisruntime.data.StatisticType;
import com.esri.arcgisruntime.data.StatisticsQueryParameters;
import com.esri.arcgisruntime.data.StatisticsQueryResult;
import com.esri.arcgisruntime.layers.FeatureLayer;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.view.MapView;

public class StatisticalQuerySample extends Application {

  private MapView mapView;

  @Override
  public void start(Stage stage) {

    try {
      // create stack pane and application scene
      StackPane stackPane = new StackPane();
      Scene scene = new Scene(stackPane);
      scene.getStylesheets().add(getClass().getResource("/statistical_query/style.css").toExternalForm());

      // set title, size, and add scene to stage
      stage.setTitle("Statistical Query Sample");
      stage.setWidth(800);
      stage.setHeight(700);
      stage.setScene(scene);
      stage.show();

      // authentication with an API key or named user is required to access basemaps and other location services
      String yourAPIKey = System.getProperty("apiKey");
      ArcGISRuntimeEnvironment.setApiKey(yourAPIKey);

      // create a map with the streets basemap style
      final ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_STREETS);

      // create a map view and set the map to it
      mapView = new MapView();
      mapView.setMap(map);

      // create a service feature table using the URL
      String featureServiceURL = "https://sampleserver6.arcgisonline" +
        ".com/arcgis/rest/services/SampleWorldCities/MapServer/0";
      final ServiceFeatureTable featureTable = new ServiceFeatureTable(featureServiceURL);

      // create a feature layer from the service feature table and add it to the map
      FeatureLayer featureLayer = new FeatureLayer(featureTable);
      map.getOperationalLayers().add(featureLayer);

      // create toggle buttons for the query filters
      CheckBox currentExtentFilterToggle = new CheckBox("Only cities in current extent");
      CheckBox populationFilterToggle = new CheckBox("Only cities greater than 5M");

      // create static definitions for all the statistics we want to query on
      // here we specify all statistic types for the "POP" (population) field
      List<StatisticDefinition> statisticDefinitions = Stream.of(StatisticType.values())
        .map(type -> new StatisticDefinition("POP", type, null))
        .collect(Collectors.toList());

      // create a button to perform the statistical query
      Button queryButton = new Button("Get Statistics");
      queryButton.setOnAction(e -> {
        // create statistics query parameters with the definitions
        StatisticsQueryParameters statisticsQueryParameters = new StatisticsQueryParameters(statisticDefinitions);

        if (currentExtentFilterToggle.isSelected()) {
          // set the query geometry to the current visible area
          statisticsQueryParameters.setGeometry(mapView.getVisibleArea());
          // set the spatial relationship to intersects (the default)
          statisticsQueryParameters.setSpatialRelationship(QueryParameters.SpatialRelationship.INTERSECTS);
        }

        if (populationFilterToggle.isSelected()) {
          // set an attribute filter to only retrieve large cities (rank = 1)
          statisticsQueryParameters.setWhereClause("POP_RANK = 1");
        }

        // execute the query
        ListenableFuture<StatisticsQueryResult> query = featureTable.queryStatisticsAsync(statisticsQueryParameters);
        query.addDoneListener(() -> {
          try {
            StatisticsQueryResult result = query.get();
            StringBuilder statistics = new StringBuilder();
            for (Iterator<StatisticRecord> it = result.iterator(); it.hasNext();) {
              StatisticRecord record = it.next();
              record.getStatistics().forEach((key, value) -> statistics.append("\n").append(key).append(": ").append(value));
            }
            Alert alert = new Alert(Alert.AlertType.INFORMATION, statistics.toString());
            alert.setHeaderText("Statistics");
            alert.show();
          } catch (ExecutionException | InterruptedException ex) {
            Alert alert = new Alert(Alert.AlertType.ERROR, ex.getMessage());
            alert.show();
          }
        });
      });

      // layout the controls
      VBox controlsVBox = new VBox(6);
      controlsVBox.setBackground(new Background(new BackgroundFill(Paint.valueOf("rgba(0,0,0,0.3)"), CornerRadii.EMPTY,
          Insets.EMPTY)));
      controlsVBox.setPadding(new Insets(10.0));
      controlsVBox.setAlignment(Pos.CENTER);
      controlsVBox.setMaxSize(220, Double.MIN_VALUE);
      controlsVBox.getStyleClass().add("panel-region");
      currentExtentFilterToggle.setMaxWidth(Double.MAX_VALUE);
      populationFilterToggle.setMaxWidth(Double.MAX_VALUE);
      queryButton.setMaxWidth(Double.MAX_VALUE);
      controlsVBox.getChildren().addAll(currentExtentFilterToggle, populationFilterToggle, queryButton);

      // add the map view and control panel to stack pane
      stackPane.getChildren().addAll(mapView, controlsVBox);
      StackPane.setAlignment(controlsVBox, Pos.TOP_LEFT);
      StackPane.setMargin(controlsVBox, new Insets(10, 0, 0, 10));

    } catch (Exception e) {
      // on any error, display the stack trace
      e.printStackTrace();
    }
  }

  /**
   * Stops and releases all resources used in application.
   */
  @Override
  public void stop() {

    if (mapView != null) {
      mapView.dispose();
    }
  }

  /**
   * Opens and runs application.
   *
   * @param args arguments passed to this application
   */
  public static void main(String[] args) {

    Application.launch(args);
  }

}

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