ZScore Rendering (Spatial Statistics)

Summary

Applies a cold (blue) to hot (red) color rendering scheme for a field of z-scores.

Illustration

Usage

• The Z Renderer creates a new layer file (.lyr) with z-scores rendered in the following manner:

  • Z-scores below –2 standard deviations are rendered dark blue.
  • Z-scores between –2 and –1 standard deviations are light blue.
  • Z-scores between –1 and +1 standard deviations are neutral.
  • Z-scores between 1 and 2 standard deviations are pink.
  • Z-scores above 2 standard deviations are bright red.

• The Z Renderer is appropriate for symbolizing standard deviations including the output from both the Hot Spot Analysis and Cluster and Outlier Analysis tools.

Legacy:

Beginning with the ArcGIS 10 release, this tool is a built-in tool (rather than a Visual Basic executable). While every effort was made not to break custom model and script tools developed prior to ArcGIS 10, there may be cases where older models that use this tool must be rebuilt in order for the model to run.

• Map layers can be used to define the Input Feature Class. When using a layer with a selection, only the selected features are included in the analysis.

Syntax

ZRenderer_stats (Input_Feature_Class, Field_to_Render, Output_Layer_File)

Parameter	Explanation	Data Type
Input_Feature_Class	The feature class containing a field with standardized z-scores.	Feature Layer
Field_to_Render	The name of the field containing the z-scores.	Field
Output_Layer_File	The new output layer file to store rendering information. You must include the .lyr extension as part of the file name.	Layer File

Code Sample

ZScore Rendering Example (Python Window)

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

import arcpy
arcpy.env.workspace = r"C:\data"
arcpy.ZRenderer_stats("hotspot_output.shp", "GiInvDst", "hotspot_output_rendered.lyr")

ZScore Rendering Example (stand-alone Python script)

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

# Perform Hot Spot Analysis for assault incidents
 
# Import system modules
import arcpy
 
# Local variables...
workspace = r"C:\data"
input = "assaults.shp"
collect_output = "collect_output.shp"
collect_count_field = "Count"
hotspot_output = "hotspot_output.shp"
hotspot_output_rendered = "hotspot_output_rendered.lyr"
z_score_field_name = "GiInvDst"
 
try:
    # Set the current workspace (to avoid having to specify the full path to the feature classes each time)
    arcpy.env.workspace = workspace
 
    # Convert assault incidents into weighted point data
    # Process: Collect Events...
    arcpy.CollectEvents_stats(input, collect_output)
 
    # Calculate Getis-Ord Gi* statistic
    # Process: Hot Spot Analysis (Getis-Ord Gi*)...
    arcpy.HotSpots_stats(collect_output, collect_count_field, hotspot_output, "INVERSE_DISTANCE", "EUCLIDEAN_DISTANCE", "NONE", "#", "#", "#")
 
    # Render hot spot analysis
    # Process: ZScore Rendering...
    arcpy.ZRenderer_stats(hotspot_output, z_score_field_name, hotspot_output_rendered)
 
except:
    # If an error occurred when running the tool, print out the error message.
    print arcpy.GetMessages(2)

Environments

Current Workspace, Scratch Workspace

Licensing Information

ArcView: Yes

ArcEditor: Yes

ArcInfo: Yes