Statistical query

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

Image of statistical query

Use case

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 queryStatisticsAsync() on the ServiceFeatureTable. Depending on the state of the two checkboxes, additional parameters are set.
  4. Display each StatisticRecord in the first returned StatisticsQueryResult.

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

MainActivity.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.arcgisruntime.sample.statisticalquery;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.concurrent.ExecutionException;

import android.os.Bundle;
import android.util.Log;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.concurrent.ListenableFuture;
import com.esri.arcgisruntime.data.FeatureTable;
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.geometry.Envelope;
import com.esri.arcgisruntime.layers.FeatureLayer;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.Viewpoint;
import com.esri.arcgisruntime.mapping.view.MapView;
import com.google.android.material.snackbar.Snackbar;

public class MainActivity extends AppCompatActivity {

  private static final String TAG = MainActivity.class.getSimpleName();

  private CheckBox mCurrentExtentCheckbox;
  private CheckBox mGreater5mCheckbox;
  private MapView mMapView;
  private FeatureTable mWorldCitiesTable;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // authentication with an API key or named user is required to access basemaps and other
    // location services
    ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY);

    // inflate ui elements
    mMapView = findViewById(R.id.mapView);
    mCurrentExtentCheckbox = findViewById(R.id.currentExtentCheckBox);
    mGreater5mCheckbox = findViewById(R.id.greater5mCheckBox);
    Button getStatisticsButton = findViewById(R.id.getStatisticsButton);

    // create a new Map with the world streets vector basemap
    ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_STREETS);

    // create feature table using the world cities URI
    mWorldCitiesTable = new ServiceFeatureTable(getString(R.string.world_cities_service_0));

    // create a new feature layer to display features in the world cities table
    FeatureLayer worldCitiesLayer = new FeatureLayer(mWorldCitiesTable);

    // add the world cities layer to the map
    map.getOperationalLayers().add(worldCitiesLayer);

    // assign the map to the MapView
    mMapView.setMap(map);

    // create definitions for each statistic to calculate and add to a list
    List<StatisticDefinition> statDefinitions = new ArrayList<>();
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.AVERAGE, ""));
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.MINIMUM, ""));
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.MAXIMUM, ""));
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.SUM, ""));
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.STANDARD_DEVIATION, ""));
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.VARIANCE, ""));
    // create a definition for count that includes an alias for the output
    statDefinitions.add(new StatisticDefinition("POP", StatisticType.COUNT, "CityCount"));

    // add click listener to get statistics button which calls getStatistics, passing in a new instance of the statistic query parameters
    getStatisticsButton.setOnClickListener(view -> {
      // create the statistics query parameters, pass in the list of definitions
      StatisticsQueryParameters statQueryParams = new StatisticsQueryParameters(statDefinitions);
      getStatistics(statQueryParams);
    });
  }

  private void getStatistics(StatisticsQueryParameters statQueryParams) {

    // if only using features in the current extent, set up the spatial filter for the statistics query parameters
    if (mCurrentExtentCheckbox.isChecked()) {
      // get the current extent (as an envelope) from the map view
      Envelope currentExtent = (Envelope) mMapView.getCurrentViewpoint(Viewpoint.Type.BOUNDING_GEOMETRY)
          .getTargetGeometry();

      // set the statistics query parameters geometry with the envelope
      statQueryParams.setGeometry(currentExtent);

      // set the spatial relationship to Intersects (which is the default)
      statQueryParams.setSpatialRelationship(QueryParameters.SpatialRelationship.INTERSECTS);
    }

    // set up an attribute filter
    if (mGreater5mCheckbox.isChecked()) {
      // set a where clause to get only cities with populations over five million
      statQueryParams.setWhereClause("POP_CLASS = '5,000,000 and greater'");
    }

    // execute the statistical query with these parameters and await the results
    ListenableFuture<StatisticsQueryResult> statQueryResultFuture = mWorldCitiesTable
        .queryStatisticsAsync(statQueryParams);
    statQueryResultFuture.addDoneListener(() -> {
      try {
        // get the result
        StatisticsQueryResult statQueryResult = statQueryResultFuture.get();

        // get iterator from the result
        Iterator<StatisticRecord> statisticRecordIterator = statQueryResult.iterator();

        // build a result string for display
        StringBuilder result = new StringBuilder();
        while (statisticRecordIterator.hasNext()) {
          Map<String, Object> statisticsMap = statisticRecordIterator.next().getStatistics();
          for (Map.Entry<String, Object> stat : statisticsMap.entrySet()) {
            result.append(stat.getKey()).append(": ")
                .append(String.format(Locale.US, "%,.0f", stat.getValue())).append("\n");
          }
        }

        // show the results in a snackbar
        Snackbar reportSnackbar = Snackbar.make(findViewById(R.id.activityMain), result, Snackbar.LENGTH_INDEFINITE);
        reportSnackbar.setAction("New Query", view -> reportSnackbar.dismiss());
        TextView snackbarTextView = reportSnackbar.getView().findViewById(com.google.android.material.R.id.snackbar_text);
        snackbarTextView.setSingleLine(false);
        reportSnackbar.show();

      } catch (InterruptedException | ExecutionException e) {
        Toast.makeText(MainActivity.this, "Error getting Statistical Query Results: " + e.getMessage(),
            Toast.LENGTH_LONG).show();
        Log.e(TAG, "Error getting Statistical Query Results: " + e.getMessage());
        e.printStackTrace();
      }
    });
  }

  @Override
  protected void onPause() {
    mMapView.pause();
    super.onPause();
  }

  @Override
  protected void onResume() {
    super.onResume();
    mMapView.resume();
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    mMapView.dispose();
  }
}

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