Directional Distribution (Standard Deviational Ellipse) (Spatial Statistics)

Summary

Creates standard deviational ellipses to summarize the spatial characteristics of geographic features: central tendency, dispersion, and directional trends.

Learn about how Directional Distribution (Standard Deviational Ellipse) works

Illustration

Directional Distribution (Standard Deviational Ellipse) graphic

Usage

Syntax

DirectionalDistribution_stats (Input_Feature_Class, Output_Ellipse_Feature_Class, Ellipse_Size, {Weight_Field}, {Case_Field})
ParameterExplanationData Type
Input_Feature_Class

A feature class containing a distribution of features for which the standard deviational ellipse will be calculated.

Feature Layer
Output_Ellipse_Feature_Class

A polygon feature class that will contain the output ellipse feature.

Feature Class
Ellipse_Size

The size of output ellipses in standard deviations. The default ellipse size is 1; valid choices are 1, 2, or 3 standard deviations.

  • 1_STANDARD_DEVIATION
  • 2_STANDARD_DEVIATIONS
  • 3_STANDARD_DEVIATIONS
String
Weight_Field
(Optional)

The numeric field used to weight locations according to their relative importance.

Field
Case_Field
(Optional)

Field used to group features for separate directional distribution calculations. The case field can be of integer, date, or string type.

Field

Code Sample

DirectionalDistribution Example (Python Window)

The following Python Window script demonstrates how to use the DirectionalDistribution tool.

import arcpy
arcpy.env.workspace = r"C:\data"
arcpy.DirectionalDistribution_stats("AutoTheft.shp", "auto_theft_SE.shp", "1_STANDARD_DEVIATION", "#", "#")
DirectionalDistribution Example (stand-alone Python script)

The following stand-alone Python script demonstrates how to use the DirectionalDistribution tool.

# Measure the geographic distribution of auto thefts
 
# Import system modules
import arcpy
 
# Local variables...
workspace = "C:/data"
locations = "AutoTheft.shp"
links = "AutoTheft_links.shp"
standardDistance = "auto_theft_SD.shp"
stardardEllipse = "auto_theft_SE.shp"
linearDirectMean = "auto_theft_LDM.shp"
 
try:
    # Set the workspace (to avoid having to type in the full path to the data every time)
    arcpy.env.workspace = workspace
 
    # Process: Standard Distance of auto theft locations...
    arcpy.StandardDistance_stats(locations, standardDistance, "1_STANDARD_DEVIATION", "#", "#")
 
    # Process: Directional Distribution (Standard Deviational Ellipse) of auto theft locations...
    arcpy.DirectionalDistribution_stats(locations, standardEllipse, "1_STANDARD_DEVIATION", "#", "#")
 
    # Process: Linear Directional Mean of auto thefts...
    arcpy.DirectionalMean_stats(links, linearDirectMean, "DIRECTION", "#")
 
except:
    # If an error occurred while running a tool, print the messages 
    print arcpy.GetMessages()

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.

Related Topics

Licensing Information

ArcView: Yes
ArcEditor: Yes
ArcInfo: Yes

3/7/2012