Perform a feature analysis

A feature analysis is the process of using the spatial analysis service to perform server-side geometric and analytic operations on feature data. All feature analysis requests are job requests. The easiest way to programmatically run an analysis request to the spatial analysis service is to use ArcGIS REST JS, which provides a Job class that handles long- running operations.

In this tutorial, you use ArcGIS REST JS to perform a hot spot analysis to find statistically significant clusters of parking violations.

Prerequisites

Steps

Get the starter code

1. Download the tutorial starter code zip file from the portal.
2. Unzip the folder and open it in a text editor of your choice, such as Visual Studio Code. The starter app includes the following:
   • callback.html: This contains callback as part of the authentication process.
   • index.html: This contains app logic and the OAuth 2.0 code necessary to perform the authentication.

Set up authentication

Create a new OAuth credential to register the application.

1. Go to the Create OAuth credentials for user authentication tutorial to get an OAuth credential.
2. Copy the Client ID and Redirect URL from your OAuth credentials item and paste them to a safe location. They will be used in a later step.

All users that access this application need an ArcGIS account with privileges to access the basemap styles service and spatial analysis service.

Set developer credentials

1. In both the index.html and callback.html files, replace YOUR_CLIENT_ID and YOUR_REDIRECT_URL with the client ID and redirect URL of your OAuth credentials.

   index.html

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         // Your client ID from OAuth credentials
         const clientId = "YOUR_CLIENT_ID";
         // The redirect URL registered in your OAuth credentials
         const redirectUri = "YOUR_REDIRECT_URL";
   
   callback.html

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         // Your client ID from OAuth credentials
         const clientId = "YOUR_CLIENT_ID";
         // The redirect URL registered in your OAuth credentials
         const redirectUri = "YOUR_REDIRECT_URL";
   

2. Run the app and ensure you can sign in successfully.

   Trouble signing in?

   If you are unable to sign in, make sure you have the correct redirect URL and port. This URL varies based on your application and typically takes the format of https://<server>[:port]/callback.html or http://my-arcgis-app:/auth. For example, if you are running an application on http://127.0.0.1:5500/, add http://127.0.0.1:5500/callback.html as your redirect URL.

Add script references

In addition to ArcGIS REST JS Request, you also reference the Portal helper class from ArcGIS REST JS to obtain the spatial analysis service URL.

1. Add references to the ArcGIS REST JS Portal helper class.

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     <!-- ArcGIS REST JS used for user authentication -->
     <script src="https://unpkg.com/@esri/arcgis-rest-request@4/dist/bundled/request.umd.js"></script>
   
     <!-- ArcGIS REST JS used for portal service -->
     <script src="https://unpkg.com/@esri/arcgis-rest-portal@4/dist/bundled/portal.umd.js"></script>
   

Get the analysis URL

To make a request to the spatial analysis service, you need to get the URL first. The analysis service URL is unique to your organization.

1. Call the getSelf operation from ArcGIS REST JS to obtain the analysis URL.

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       const getAnalysisUrl = async (session) => {
         const portalSelf = await arcgisRest.getSelf({
           authentication: session,
         });
   
         return portalSelf.helperServices.analysis.url;
       };
   

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Make the request

Use the Job class and set the operationURL and params required for the selected analysis.

1. Add the parking violations feature layer to the points variable. This feature layer is the input data for the hot spot analysis.

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       const points =
         "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/sf_traffic_parking_violations_sa_osapi/FeatureServer/0";
   

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2. Create a function that submits a Job request to the spatial analysis service using your organization's analysis URL. Set the params required for a hot spot analysis and authenticate using the session token.

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       const runAnalysis = async () => {
         const analysisUrl = await getAnalysisUrl(session);
         const operationUrl = `${analysisUrl}/FindHotSpots/submitJob`;
         const params = {
           analysisLayer: { url: points },
           shapeType: 'Hexagon',
           outputName: {
             serviceProperties: {
               name: `RestJS_find_hot_spots_${new Date().getTime()}`,
             },
           }, //Outputs results as a hosted feature serivce.
         };
   
         const jobReq = await arcgisRest.Job.submitJob({
           url: operationUrl,
           params: params,
           authentication: session,
         });
   
         // listen to the status event to get updates every time the job status is checked.
         jobReq.on(arcgisRest.JOB_STATUSES.Status, (jobInfo) => {
           console.log(jobInfo.status);
         });
   
         // get all the results, this will start monitoring and trigger events
         const jobResp = await jobReq.getAllResults();
   
         // jobResp.aggregatedLayer.value.url
         return jobResp;
       };
   
   

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3. Call the runAnalysis function and store its result in the jobResponse variable.

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       const runAnalysis = async () => {
         const analysisUrl = await getAnalysisUrl(session);
         const operationUrl = `${analysisUrl}/FindHotSpots/submitJob`;
         const params = {
           analysisLayer: { url: points },
           shapeType: 'Hexagon',
           outputName: {
             serviceProperties: {
               name: `RestJS_find_hot_spots_${new Date().getTime()}`,
             },
           }, //Outputs results as a hosted feature serivce.
         };
   
         const jobReq = await arcgisRest.Job.submitJob({
           url: operationUrl,
           params: params,
           authentication: session,
         });
   
         // listen to the status event to get updates every time the job status is checked.
         jobReq.on(arcgisRest.JOB_STATUSES.Status, (jobInfo) => {
           console.log(jobInfo.status);
         });
   
         // get all the results, this will start monitoring and trigger events
         const jobResp = await jobReq.getAllResults();
   
         // jobResp.aggregatedLayer.value.url
         return jobResp;
       };
   
       const jobResponse = await runAnalysis()
   

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Handle the results

The results of a feature analysis are returned as feature data.

1. Print out the URL of the resulting hosted feature layer.

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       console.log(`Resulting layer from hot spot analysis: ${jobResponse.hotSpotsResultLayer.value.url}`)
   

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Run the app

Run the application and navigate to your localhost, for example: https://localhost:8080.

Once you are successfully authenticated, you submit a request to the spatial analysis service to perform a hot spot analysis. When the job is complete, you can use the URL of the resulting feature layer in the app. The metadata of the layer will look something like this:

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{
  "currentVersion": 11,
  "id": 0,
  "name": "HotSpotsLayer",
  "type": "Feature Layer",
  "serviceItemId": "898aacb4ea5c4b00b4a51c634f268459",
  "cacheMaxAge": 30,
  "displayField": "",
  "description": "",
  "copyrightText": "",
  "defaultVisibility": true,
  "editingInfo": {
    "lastEditDate": 1667488958822,
    "schemaLastEditDate": 1667488958822,
    "dataLastEditDate": 1667488958822
  },
  "relationships": [],
  "isDataVersioned": false,
  "hasContingentValuesDefinition": false,
  "supportsAppend": true,
  "supportsCalculate": true,
  "supportsASyncCalculate": true,
  "supportsTruncate": true,
  "supportsAttachmentsByUploadId": true,
  "supportsAttachmentsResizing": true,
  "supportsRollbackOnFailureParameter": true,
  "supportsStatistics": true,
  "supportsExceedsLimitStatistics": true,
  "supportsAdvancedQueries": true,
  "supportsValidateSql": true,

What's next?

To learn how to perform other types of feature analysis, go to the related tutorials in the Spatial analysis guide:

Find and extract data

Find data with attribute and spatial queries using find analysis operations.

Combine data

Overlay, join, and dissolve features using combine analysis operations.

Summarize data

Aggregate and summarize features using summarize analysis operations.

Discover patterns in data

Find patterns and trends in data using spatial analysis operations.