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ArcGIS Runtime SDK for .NET

Analyze hotspots

This code sample is available for these platforms:
View Sample on GitHub

Use a geoprocessing service and a set of features to identify statistically significant hot spots and cold spots.

Image of analyze hotspots

Use case

This tool identifies statistically significant spatial clusters of high values (hot spots) and low values (cold spots). For example, a hotspot analysis based on the frequency of 911 calls within a set region.

How to use the sample

Select a date range (between 1998-01-01 and 1998-05-31) from the dialog and tap on Analyze. The results will be shown on the map upon successful completion of the GeoprocessingJob.

How it works

  1. Create a GeoprocessingTask with the URL set to the endpoint of a geoprocessing service.
  2. Create a query string with the date range as an input of GeoprocessingParameters.
  3. Use the GeoprocessingTask to create a GeoprocessingJob with the GeoprocessingParameters instance.
  4. Start the GeoprocessingJob and wait for it to complete and return a GeoprocessingResult.
  5. Get the resulting ArcGISMapImageLayer using GeoprocessingResult.MapImageLayer.
  6. Add the layer to the map's operational layers.

Relevant API

  • GeoprocessingJob
  • GeoprocessingParameters
  • GeoprocessingResult
  • GeoprocessingTask

Tags

Geoprocessing, GeoprocessingJob, GeoprocessingParameters, GeoprocessingResult

Sample Code

<?xml version="1.0" encoding="utf-8"?>

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:esriUI="clr-namespace:Esri.ArcGISRuntime.Xamarin.Forms;assembly=Esri.ArcGISRuntime.Xamarin.Forms"
             x:Class="ArcGISRuntime.Samples.AnalyzeHotspots.AnalyzeHotspots">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Label Text="Start date:"
               Grid.Row="0" Grid.Column="0"
               HorizontalTextAlignment="Start"
               VerticalTextAlignment="Center"/>
        <DatePicker x:Name="StartDate" Date="1/01/98"
                    Grid.Row="0" Grid.Column="1" />
        <Label Text="End date:"
               Grid.Row="1" Grid.Column="0"
               HorizontalTextAlignment="Start"
               VerticalTextAlignment="Center"/>
        <DatePicker x:Name="EndDate" Date="1/31/98"
                    Grid.Row="1" Grid.Column="1" />
        <Button Text="Run Analysis"
                Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="2"
                Clicked="OnRunAnalysisClicked" />
        <ActivityIndicator x:Name="MyActivityIndicator"
                           Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="2"
                           IsVisible="False" />
        <esriUI:MapView x:Name="MyMapView"
                        Grid.Row="4" Grid.Column="0" Grid.ColumnSpan="2" />
    </Grid>
</ContentPage>
// Copyright 2016 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.Mapping;
using Esri.ArcGISRuntime.Tasks;
using Esri.ArcGISRuntime.Tasks.Geoprocessing;
using System;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace ArcGISRuntime.Samples.AnalyzeHotspots
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Analyze hotspots",
        category: "Geoprocessing",
        description: "Use a geoprocessing service and a set of features to identify statistically significant hot spots and cold spots.",
        instructions: "Select a date range (between 1998-01-01 and 1998-05-31) from the dialog and tap on Analyze. The results will be shown on the map upon successful completion of the `GeoprocessingJob`.",
        tags: new[] { "Geoprocessing", "GeoprocessingJob", "GeoprocessingParameters", "GeoprocessingResult" })]
    public partial class AnalyzeHotspots : ContentPage
    {

        // Url for the geoprocessing service
        private const string _hotspotUrl =
            "https://sampleserver6.arcgisonline.com/arcgis/rest/services/911CallsHotspot/GPServer/911%20Calls%20Hotspot";

        // The geoprocessing task for hot spot analysis 
        private GeoprocessingTask _hotspotTask;

        // The job that handles the communication between the application and the geoprocessing task
        private GeoprocessingJob _hotspotJob;

        public AnalyzeHotspots()
        {
            InitializeComponent();

            // Create the UI, setup the control references and execute initialization 
            Initialize();
        }

        private async void Initialize()
        {
            // Create a map with a topographic basemap
            MyMapView.Map = new Map(Basemap.CreateTopographic());

            try
            {
                // Create a new geoprocessing task
                _hotspotTask = await GeoprocessingTask.CreateAsync(new Uri(_hotspotUrl));
            }
            catch (Exception e)
            {
                await Application.Current.MainPage.DisplayAlert("Error", e.ToString(), "OK");
            }
        }

        private async void OnRunAnalysisClicked(object sender, EventArgs e)
        {
            // Clear any existing results
            MyMapView.Map.OperationalLayers.Clear();

            // Show busy activity indication
            MyActivityIndicator.IsVisible = true;
            MyActivityIndicator.IsRunning = true;

            // The end date must be at least one day after the start date
            if (EndDate.Date <= StartDate.Date.AddDays(1))
            {
                // Show error message
                await Application.Current.MainPage.DisplayAlert("Invalid date range", "Please select valid time range. There has to be at least one day in between To and From dates.", "OK");

                // Remove the busy activity indication
                MyActivityIndicator.IsRunning = false;
                MyActivityIndicator.IsVisible = false;
                return;
            }

            // Create the parameters that are passed to the used geoprocessing task
            GeoprocessingParameters myHotspotParameters = new GeoprocessingParameters(GeoprocessingExecutionType.AsynchronousSubmit);

            // Construct the date query
            string myQueryString = $"(\"DATE\" > date '{StartDate.Date:yyyy-MM-dd} 00:00:00' AND \"DATE\" < date '{EndDate.Date:yyyy-MM-dd} 00:00:00')";

            // Add the query that contains the date range used in the analysis
            myHotspotParameters.Inputs.Add("Query", new GeoprocessingString(myQueryString));

            // Create job that handles the communication between the application and the geoprocessing task
            _hotspotJob = _hotspotTask.CreateJob(myHotspotParameters);
            try
            {
                // Execute the geoprocessing analysis and wait for the results
                GeoprocessingResult myAnalysisResult = await _hotspotJob.GetResultAsync();

                // Add results to a map using map server from a geoprocessing task
                // Load to get access to full extent
                await myAnalysisResult.MapImageLayer.LoadAsync();

                // Add the analysis layer to the map view
                MyMapView.Map.OperationalLayers.Add(myAnalysisResult.MapImageLayer);

                // Zoom to the results
                await MyMapView.SetViewpointAsync(new Viewpoint(myAnalysisResult.MapImageLayer.FullExtent));
            }
            catch (TaskCanceledException)
            {
                // This is thrown if the task is canceled. Ignore.
            }
            catch (Exception ex)
            {
                // Display error messages if the geoprocessing task fails
                if (_hotspotJob.Status == JobStatus.Failed && _hotspotJob.Error != null)
                {
                    await Application.Current.MainPage.DisplayAlert("Geoprocessing error", "Executing geoprocessing failed. " + _hotspotJob.Error.Message, "OK");
                }
                else
                {
                    await Application.Current.MainPage.DisplayAlert("Sample error", "An error occurred. " + ex.ToString(), "OK");
                }
            }
            finally
            {
                // Remove the busy activity indication
                MyActivityIndicator.IsRunning = false;
                MyActivityIndicator.IsVisible = false;
            }
        }
    }
}