Extract by Attributes (Spatial Analyst)

Summary

Extracts the cells of a raster based on a logical query.

Illustration

OutRas = ExtractByAttributes(InRas1, "Value > 0")

Usage

• Additional attributes from the input raster, if any, will be carried over as-is to the output raster attribute table. Depending on the property being recorded, some of the attribute values may need to be recalculated.

• When a multiband raster is specified as the Input Raster (in_raster in Python) value, all bands will be used.

  To process a selection of bands from a multiband raster, first create a raster dataset composed of those particular bands using the Composite Bands tool. Then use the result as the Input Raster (in_raster in Python) value.

  The default output format is a geodatabase raster. If an Esri Grid stack is specified as the output format, the name of the stack cannot start with a number, use spaces, or be more than nine characters in length.

• If the Where clause evaluates to true, the original input value is returned for the cell location. If it evaluates to false, the cell location is assigned NoData.

• The Where clause uses an SQL query. See the following topics for more details on creating queries:

  • Build an SQL query
  • SQL reference for query expressions used in ArcGIS

• In order to use a {where_clause} in Python, it should be enclosed in quotes. For example, "Value > 5000".

  You can consult the help for more information on specifying a query in Python.

• If an item other than Value of input raster is specified in the query, the original input value is returned for the cell location.

• If the input raster is integer, the output raster will be integer. If the input is floating point, the output will be floating point.

• See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

Parameters

Dialog

Label	Explanation	Data Type
Input raster	The input raster from which cells will be extracted.	Raster Layer
Where clause	A logical expression that selects a subset of raster cells. The Where clause follows the general form of an SQL expression. It can be entered directly, for example, VALUE > 100, if you click the Edit SQL mode button . If in the Edit Clause Mode , you can begin constructing the expression by clicking on the Add Clause Mode button.	SQL Expression

Return Value

Label	Explanation	Data Type
Output raster	The output raster containing the cell values extracted from the input raster.	Raster

Python

ExtractByAttributes(in_raster, where_clause)

Name	Explanation	Data Type
in_raster	The input raster from which cells will be extracted.	Raster Layer
where_clause	A logical expression that selects a subset of raster cells. The expression follows the general form of an SQL expression. An example of a where_clause is "VALUE > 100".	SQL Expression

Return Value

Name	Explanation	Data Type
out_raster	The output raster containing the cell values extracted from the input raster.	Raster

Code sample

ExtractByAttributes example 1 (Python window)

This example extracts cells from a raster based on a logical query, where elevation is greater than 1,000 meters.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
attExtract = ExtractByAttributes("elevation", "VALUE > 1000") 
attExtract.save("c:/sapyexamples/output/attextract")

ExtractByAttributes example 2 (stand-alone script)

This example extracts cells from a raster based on a logical query, where elevation is greater than 1,000 meters.

# Name: ExtractByAttributes_Ex_02.py
# Description: Extracts the cells of a raster based on a logical query. 
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inRaster = "elevation"
inSQLClause = "VALUE > 1000"

# Execute ExtractByAttributes
attExtract = ExtractByAttributes(inRaster, inSQLClause) 

# Save the output 
attExtract.save("c:/sapyexamples/output/attextract02")

Environments

Auto Commit, Cell Size, Cell Size Projection Method, Compression, Current Workspace, Extent, Geographic Transformations, Mask, Output CONFIG Keyword, Output Coordinate System, Scratch Workspace, Snap Raster, Tile Size