Find Outliers

analysisLayer

(Required)

The point or polygon feature layer for which outliers 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 analysisLayer contains polygons)

The numeric field that will be analyzed. This field can represent the following:

• 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 value is not provided, hot spot results will be based on point densities only.

Syntax: "analysisField": "Average_Score"

dividedByField

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

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

Syntax: "dividedByField": "esriPopulation"

boundingPolygonLayer

When the analysis layer is points and no analysisField value is provided, you can provide polygon features that define where incidents could have occurred. For example, if you are analyzing boating accidents in a harbor, the outline of the harbor can provide a 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 value contains points and no analysisField value 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

permutations

Specifies the type of permutations that will be used. Permutations are used to determine how likely it would be to find the actual spatial distribution of the values you are analyzing. Deciding on the number of permutations is a balance between precision and increased processing time. A lower number of permutations can be used when first exploring a problem, but it is a best practice to increase the permutations to the highest number feasible for final results.

• Speed—Implements 199 permutations and results in p-values with a precision of 0.005
• Balance—Implements 499 permutations and results in p-values with a precision of 0.002
• Precision—Implements 999 permutations and results in p-values with a precision of 0.001

Values: Speed | Balance | Precision

Example: "permutations": "Precision"

shapeType

Specifies 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 that will be used to aggregate the features. When aggregating into a hexagon grid, this distance is used as the height to construct the hexagon polygons.

Example: "cellSize": 500

cellSizeUnits

Specifies the units of the cellSize value. You must specify a value if a value for cellSize has been set.

Values: Miles | Feet | Kilometers | Meters

Example: "cellSizeUnits": "Meters"

distanceBand

The spatial extent of the analysis neighborhood. This value determines which features will be analyzed together to assess local clustering.

distanceBandUnits

Specifies the units of the distanceBand value. You must specify a value if a value for distanceBand has been set.

Values: Miles | Feet | Kilometers | Meters

Example: "distanceBandUnits": "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.
• Random number seed (randomGenerator)—A string representing the integer and seed type that will initiate a random number generator. The seed type is always MERSENNE_TWISTER, for example, 13 MERSENNE_TWISTER. This parameter is available in ArcGIS Enterprise 11.2 or later.

Syntax:

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{
"extent" : {extent},
"outSR" : {"wkid": 4326},
"randomGenerator" : "13 MERSENNE_TWISTER"
}

f

The response format. The default response format is html.

Values: html | json

outlierResultLayer

The result of the FindOutliers task is a feature layer that provides information about statistically significant outlier features.

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

The result layer has the following attributes:

• ID field (FID)—An integer field with a unique value for every feature.
• AnalysisField or Join_Count—When an analysisField value is provided, it will be copied to the result with the same name and properties. When no analysisField value is provided, an integer field is created with values reflecting the number of points in each aggregation polygon. If an aggregationPolygonLayer value is provided, the polygons are used for aggregation. Otherwise, a fishnet or hexagon 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—A 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 the features should be drawn in white or beige (the color should be neutral to not draw attention).

Example:

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{"url":"http://<analysis url>/FindOutliers/jobs/<jobId>/results/outlierResultLayer"}

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

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

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

• If no outputName value was provided, value contains a feature collection.

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

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

processInfo

Contains strings that describe the workflow used by FindOutliers when calculating the result. These strings are used for reporting by the Find Outliers tool in Map Viewer in ArcGIS Online. You can create 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 contain parameters (in ${paramsName} format) that must be replaced by values
• params—A dictionary of the keys and values to be inserted into ${paramsName} in the message
• style—The style used to format the report produced by the Find Outliers tool in Map Viewer.

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>",
}