Summarize center and dispersion

What is a center and dispersion analysis?

A center and dispersion analysis is the process of finding center features and directional distribution in feature data. It calculates the central, mean center, median center, or ellipse of features. To execute the analysis, use the spatial analysis service and the SummarizeCenterAndDispersion operation.

Real-world examples of this analysis include the following:

• Finding the directional distribution of pest infestations.
• Selecting the best place to open a library or other point of interest.
• Finding the center of incidents of traffic crashes or crimes.

How to perform a center and dispersion analysis?

The general steps to performing summarize center and dispersion analysis are as follows:

1. Review the parameters for the SummarizeCenterAndDispersion operation.
2. Send a request to get the spatial analysis service URL.
3. Execute a job request with the following URL and parameters:
   • URL: http://<YOUR_ANALYSIS_SERVICE>/arcgis/rest/services/tasks/GPServer/SummarizeCenterAndDispersion/submitJob
   • Parameters:
     • analysisLayer: The point, line, or polygon features to be analyzed.
     • summarizeType: CentralFeature | MeanCenter | MedianCenter | Ellipse.
     • outputName: A string representing the name of the hosted feature layer to reutrn with the results.
4. Check the status.
5. Get the output layer results.

To see examples using ArcGIS API for Python, ArcGIS REST JS, and the ArcGIS REST API, go to Examples below.

URL Request

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http://<YOUR_ANALYSIS_SERVICE>/arcgis/rest/services/tasks/GPServer/SummarizeCenterAndDispersion/submitJob?<parameters>

Required parameters

Key parameters

Example

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analysisLayer = {
    "url": "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/PST_IF_PT_point/FeatureServer/0",
    "filter": "(PST_CMN_NM = 'Douglas-fir Beetle') AND (CPTR_YR >= 2020)",
}

results = summarize_center_and_dispersion(
    analysis_layer=analysisLayer,
    summarize_type=["CentralFeature", "MeanCenter", "MedianCenter", "Ellipse"],
    weight_field="NUM_TREES",
    ellipse_size="1 standard deviation",
    output_name="Summarize dispersion results", #Outputs results as a hosted feature layer.
    context={
        "overwrite": True,
        "extent": {
            "xmin": -15034729.266472297,
            "ymin": 5716733.479048933,
            "xmax": -12070195.56146081,
            "ymax": 7808050.572930799,
            "spatialReference": {"wkid": 102100, "latestWkid": 3857},
        },
    },
)

result_features = results["ellipse_result_layer"].query()

print(
    f"summarize result layer contains {len(result_features.features)} records"
)

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POST arcgis.com/sharing/rest/portals/self HTTP/1.1
Content-Type: application/x-www-form-urlencoded

&f=json
&token=<ACCESS_TOKEN>

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{
  "helperServices": {
    // Other parameters
    "analysis": {
      "url": "https://<YOUR_ANALYSIS_SERVICE>/arcgis/rest/services/tasks/GPServer"
    },
    "geoenrichment": {
      "url": "https://geoenrich.arcgis.com/arcgis/rest/services/World/GeoenrichmentServer"
    }
  }
}

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POST <YOUR_ANALYSIS_SERVICE>/arcgis/rest/services/tasks/GPServer/SummarizeCenterAndDispersion/submitJob HTTP/1.1
Content-Type: application/x-www-form-urlencoded

token=<ACCESS_TOKEN>
&f=json
&analysisLayer={"url":"https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/PST_IF_PT_point/FeatureServer/0","filter":"(PST_CMN_NM = 'Douglas-fir Beetle') AND (CPTR_YR >= 2020)"}
&summarizeType=["CentralFeature","MeanCenter","MedianCenter","Ellipse"]
&weightField=NUM_TREES
&ellipseSize=1 standard deviation
&context={"extent":{"xmin":-15034729.266472297,"ymin":5716733.479048933,"xmax":-12070195.56146081,"ymax":7808050.572930799,"spatialReference":{"wkid":102100,"latestWkid":3857}}}&outputName={"serviceProperties":{"name":"SumCenterDispersion_Result_PM"}}
&outputName={"serviceProperties":{"name":"Summarize dispersion results"}}

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{
  "jobId": "<JOB_ID>",
  "jobStatus": "esriJobSubmitted",
  "results": {},
  "inputs": {},
  "messages": []
}

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POST <YOUR_ANALYSIS_SERVICE>/arcgis/rest/services/tasks/GPServer/SummarizeCenterAndDispersion/jobs/<JOB_ID> HTTP/1.1
Content-Type: application/x-www-form-urlencoded

f=json
&token=<ACCESS_TOKEN>

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{
  "jobId": "<JOB_ID>",
  "jobStatus": "esriJobSucceeded",
  "results": {
    "centralFeatureResultLayer": {
      "paramUrl": "results/centralFeatureResultLayer"
    },
    "meanCenterResultLayer": {
      "paramUrl": "results/meanCenterResultLayer"
    },
    "medianCenterResultLayer": {
      "paramUrl": "results/medianCenterResultLayer"
    },
    "ellipseResultLayer": {
      "paramUrl": "results/ellipseResultLayer"
    }
  },
  "inputs": {},
  "messages": []
}

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POST <YOUR_ANALYSIS_SERVICE>/arcgis/rest/services/tasks/GPServer/SummarizeCenterAndDispersion/jobs/<JOB_ID>/results/ellipseResultLayer HTTP/1.1
Content-Type: application/x-www-form-urlencoded

f=json
&token=<ACCESS_TOKEN>

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{
  "paramName": "ellipseResultLayer",
  "dataType": "GPString",
  "value": {
    "url": "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/SumCenterDispersion_Result_PM/FeatureServer/3",
    "itemId": "9dacd976ec4644f5988e0b922d6bcb5b"
  }
}

Tutorials

Learn how to perform related analyses interactively with Map Viewer and programmatically with ArcGIS API for Python, ArcGIS REST JS, and ArcGIS REST API.

Summarize data

Aggregate and summarize features using summarize analysis operations.

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