Collect Events (Spatial Statistics)

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Summary

Converts event data, such as crime or disease incidents, to weighted point data.

Illustration

Collect Events tool illustration

Usage

  • Collect Events combines coincident points: it creates a new Output Feature Class containing all of the unique locations found in the Input Feature Class. It then adds a field named ICOUNT to hold the sum of all incidents at each unique location.

  • This tool will only combine features that have the exact same X and Y centroid coordinates. You may want to use the Integrate tool to snap nearby features together prior to running the Collect Events tool.

    Caution:

    The Integrate tool permanently alters feature geometry; always make a backup copy of your feature class prior to using Integrate.

  • The Hot Spot Analysis (Getis-Ord Gi*), Cluster and Outlier Analysis (Local Moran's I), and Spatial Autocorrelation (Morans I) tools, for example, require weighted points rather than individual incidents. Collect Events can be used to create weights when the input feature class contains coincident features.

  • Although this tool will work with polygon or line data, it is really only appropriate for event, incident, or other point feature data. For line and polygon features, feature coincidence is based on feature true geometric centroids. For multipoint, polyline, or polygons with multiple parts, the centroid is computed using the weighted mean center of all feature parts. The weighting for point features is 1, for line features is length, and for polygon features is area.

  • When the Input Feature Class is not projected (that is, when coordinates are given in degrees, minutes, and seconds) or when the output coordinate system is set to a Geographic Coordinate System, distances are computed using chordal measurements. Chordal distance measurements are used because they can be computed quickly and provide very good estimates of true geodesic distances, at least for points within about thirty degrees of each other. Chordal distances are based on an oblate spheroid. Given any two points on the earth's surface, the chordal distance between them is the length of a line, passing through the three-dimensional earth, to connect those two points. Chordal distances are reported in meters.

    Caution:

    Be sure to project your data if your study area extends beyond 30 degrees. Chordal distances are not a good estimate of geodesic distances beyond 30 degrees.

  • If you want each individual point/part of multipoint/multipart data treated as singlepart features, run the Multipart to Singlepart tool, then run Collect Events on the single part feature class. For more information, see Processing Multipoint Data.

  • In addition to the Output Feature Class, this function passes, as derived output values, the name of the count field and the maximum count value encountered for any one location. These derived output values are helpful when you use this tool in models or scripts.

  • When this tool runs in ArcMap, the output feature class is automatically added to the Table of Contents (TOC) with default rendering applied to the ICOUNT field. The graduated circle rendering is defined by a layer file in <ArcGIS Pro>\Resources\ArcToolBox\Templates\Layers. You can reapply the default rendering, if needed, by re-applying the layer symbology.

Parameters

LabelExplanationData Type
Input Incident Features

The features representing event or incident data.

Feature Layer
Output Weighted Point Feature Class

The output feature class to contain the weighted point data.

Feature Class

Derived Output

LabelExplanationData Type
Results Field

The name of the count field

Field
Z Max Value

The maximum count value encountered for any one location.

Double

Environments

Output Coordinate System

Feature geometry is projected to the Output Coordinate System prior to analysis. All mathematical computations are based on the Output Coordinate System spatial reference.

Licensing information

  • Basic: Yes
  • Standard: Yes
  • Advanced: Yes

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