Find Hot Spots

analysisLayer (Required)

The point or polygon feature layer for which hot spots will be calculated.

Syntax: As described in detail in the Feature input topic, this parameter can be one of the following:

• A URL to a feature service layer with an optional filter to select specific features
• A feature collection

Examples:

• {"url": <feature service layer url>, "filter": <where clause>}
• {"layerDefinition": {}, "featureSet": {}, "filter": <where clause>}

analysisField (Required if the analysisLayer contains polygons)

The numeric field that will be analyzed. The field you select might represent:

• counts (such as the number of traffic accidents)
• rates (such as the number of crimes per square mile)
• averages (such as the mean math test score)
• indices (such as a customer satisfaction score)

If an analysisField is not supplied, hot spot results are based on point densities only.

Syntax: "analysisField": "Average_Score"

divideByField

The numeric field in the analysisLayer that will be used to normalize your data. For example, if your points represent crimes, dividing by total population would result in an analysis of crimes per capita rather than raw crime counts.

You can use esriPopulation to geoenrich each area feature with the most recent population values, which will then be used as the attribute to divide by. This option will use credits.

Syntax: "divideByField": "esriPopulation"

boundingPolygonLayer

When the analysis layer is points and no analysisField is specified, you can provide polygons features that define where incidents could have occurred. For example, if you are analyzing boating accidents in a harbor, the outline of the harbor might provide a good boundary for where accidents could occur. When no bounding areas are provided, only locations with at least one point will be included in the analysis.

Syntax: As described in detail in the Feature input topic, this parameter can be one of the following:

• A URL to a feature service layer with an optional filter to select specific features
• A feature collection

aggregationPolygonLayer

When the analysisLayer contains points and no analysisField is specified, you can provide polygon features into which the points will be aggregated and analyzed, such as administrative units. The number of points that fall within each polygon are counted, and the point count in each polygon is analyzed.

Syntax: As described in detail in the Feature input topic, this parameter can be one of the following:

• A URL to a feature service layer with an optional filter to select specific features
• A feature collection

shapeType

The shape of the polygon mesh the input features will be aggregated into.

• Fishnet—The input features will be aggregated into a grid of square (fishnet) cells.
• Hexagon—The input features will be aggregated into a grid of hexagonal cells.

Example: "shapeType": "Hexagon"

cellSize

The size of the grid cells used to aggregate your features. When aggregating into a hexagon grid, this distance is used as the height to construct the hexagon polygons.

Example: "cellSize": 500

cellSizeUnits

The units of the cellSize value. You must provide a value if cellSize has been set.

Values: Miles | Feet | Kilometers | Meters

Example:"cellSizeUnit": "Meters"

distanceBand

The spatial extent of the analysis neighborhood. This value determines which features are analyzed together in order to assess local clustering.

distanceBandUnits

The units of the distanceBand value. You must provide a value if distanceBand has been set.

Values: Miles | Feet | Kilometers | Meters

Example:"distanceBandUnit": "Meters"

outputName

If provided, the task will create a feature service of the results. You define the name of the service. If an outputName value is not provided, the task will return a feature collection.

Syntax:

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{
  "serviceProperties": {
    "name": "<service name>"
  }
}

In ArcGIS Online or ArcGIS Enterprise 11.1 and later, you can overwrite an existing feature service by providing the itemId value of the existing feature service and setting the overwrite property to true. Including the serviceProperties parameter is optional. As described in the Feature output topic, you must either be the owner of the feature service or have administrative privileges to perform the overwrite.

Syntax:

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{

  "itemProperties": {
			"itemId": "<itemID of the existing feature service>",
			"overwrite": true
	}
}

or

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{
"serviceProperties": {
    "name": "<existing service name>"
  },
"itemProperties": {
				"itemId": "<itemID of the existing feature service>",
				"overwrite": true
	}
}

The processInfo parameter and pop-ups are not updated by overwriting the output feature layer if the existing output feature layer already has strings for processInfo and custom pop-ups.

context

The Context parameter contains the following additional settings that affect task operation:

• Extent (extent)—A bounding box that defines the analysis area. Only input features that intersect the bounding box will be analyzed.
• Output spatial reference (outSR)—The output features will be projected into the output spatial reference.

Syntax:

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{
  "extent" : {extent},
  "outSR" : {spatial reference}
}

f

The response format. The default response format is html.

Values: html | json

hotSpotsResultLayer

The result of Find Hot Spots is a feature layer that provides information about statistically significant hot and cold features.

If the input analysis layer (analysisLayer) contains points and an analysisField is specified, the result will be points. For all other scenarios (polygons or points when no analysisField is specified) the output is polygons.

The result layer has the following attributes:

• An ID field (FID)—An Integer field with a unique value for every feature.
• AnalysisField or Join_Count —When an analysisField is specified, it will be copied to the result with the same name a properties. When no analysisField is specified, an Integer field is created with values reflecting the number of points in each aggregation polygon. If an aggregationPolygonLayer is specified, these polygons are used for aggregation. Otherwise, a fishnet polygon mesh is created to overlay the points, and the squares in the fishnet mesh are used as aggregation polygons.
• Hot/Cold Intensity—a numeric (double) field with standard deviations representing the intensity of spatial clustering.
• Confidence Bin—use this field for symbolizing the results. Values range from -3 to +3 and reflect statistical significance. Use blue to draw values less than zero and red to draw values greater than zero. Use the darkest blue for features equal to -3, medium blue for -2, and light blue for -1. Use the darkest red for features equal to 3, medium red for 2, and the lightest red or pink for 1. A confidence bin value of zero means no statistically significant clustering, and these features should be draw in white or beige (the color selected should be neutral and not draw attention at all).

Example:

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{"url":"http://<analysis url>/FindHotSpots/jobs/<jobId>/results/hotSpotResultLayer"}

The result has properties for parameter name, data type, and value. The contents of value depends on the outputName parameter provided in the initial request.

• If outputName was provided, value contains the URL to the feature service layer.

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{
"paramName":"hotSpotResultLayer",
"dataType":"GPString",
"value":{"url":"<hosted featureservice layer url>"}
}

• If outputName was not provided, value contains a feature collection.

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{
"paramName": "hotSpotResultLayer",
"dataType": "GPString",
"value":{"layerDefinition": {}, "featureSet": {} }
}

See Feature Output for more information about how the result layer or collection is accessed.

processInfo

processInfo contains strings that describe the workflow used by Find Hot Spots when calculating the result. These strings are used for reporting by the Find Hot Spots tool in Map Viewer Classic. You can create your own custom reports for your application using these strings. There are four parts in the returned JSON:

• messageCode—The serial number for each unique message.
• message—Text that may or may not contain parameters (in ${paramsName} format) that need to be replaced by values.
• params—Dictionary of the keys and values to be inserted into the ${paramsName} in the message.
• style—For formatting of the report produced by the Find Hot Spots tool found in the ArcGIS Online Map Viewer Classic.

Example:

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{
"messageCode" : "SS_84464",
"message" : "The optimal fixed distance band is based on the average distance to ${NumNeighs} nearest neighbors: ${DistanceInfo}",
"params" : { "NumNeighs" : "20" , "DistanceInfo" : "446.8956 Meters" },
"style" : "<ul><li></li></ul><br></br>",
}