Set Null (Spatial Analyst)

Summary

Set Null sets identified cell locations to NoData based on a specified criteria. It returns NoData if a conditional evaluation is true, and returns the value specified by another raster if it is false.

Learn more about setting cell values to NoData with Set Null

Illustration

OutRas = SetNull(InRas1, InRas2, "Value = 4")

Usage

• If the evaluation of the where clause is true, the cell location on the output raster will be assigned NoData. If the evaluation is false, the output raster will be defined by the input false raster or constant value.

• If no where clause is specified, the output raster will have NoData wherever the conditional raster is not 0.

• The input conditional raster does not affect whether the output data type is integer or floating point. If the input false raster (or constant value) contains floating-point values, the output raster will be floating point. If it contains all integer values, the output will be an integer raster.

• If the Input conditional raster (in_conditional_raster in Python) is a single-band raster and the Input false raster or constant value (in_false_raster_or_constant In Python) raster is a constant, the output will be a single-band raster.

• If both inputs are multiband rasters, the output will be a multiband raster. The output raster will also be multiband if the false raster input is a constant. The number of bands in each multiband input must be the same.

• The tool will perform the operation on each band from the conditional raster using the corresponding band from the other input. If the conditional input is a multiband raster and the false raster input is a constant, the tool will perform the operation using the constant value for each band in the multiband input.

• The Expression 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.

• The maximum length of the logical expression is 4,096 characters.

Parameters

Dialog

Label	Explanation	Data Type
Input conditional raster	The input raster representing the true or false result of the desired condition. It can be of integer or floating point type.	Raster Layer
Input false raster or constant value	The input whose values will be used as the output cell values if the condition is false. It can be an integer or a floating-point raster, or a constant value.	Raster Layer; Constant
Expression (Optional)	A logical expression that determines which of the input cells are to be true or false. 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. If the conditional evaluation is true, NoData is returned. If false, the value of the second input raster is returned.	Raster

Python

SetNull(in_conditional_raster, in_false_raster_or_constant, {where_clause})

Name	Explanation	Data Type
in_conditional_raster	The input raster representing the true or false result of the desired condition. It can be of integer or floating point type.	Raster Layer
in_false_raster_or_constant	The input whose values will be used as the output cell values if the condition is false. It can be an integer or a floating-point raster, or a constant value.	Raster Layer; Constant
where_clause (Optional)	A logical expression that determines which of the input cells are to be true or false. 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. If the conditional evaluation is true, NoData is returned. If false, the value of the second input raster is returned.	Raster

Code sample

SetNull example 1 (Python window)

In this example, any input cell with a value less than 0 will be set to NoData in the output raster, and the remaining cells will retain their original value.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outSetNull = SetNull("elevation", "elevation", "VALUE < 0")
outSetNull.save("C:/sapyexamples/output/outsetnull.img")

SetNull example 2 (stand-alone script)

In this example, any input cell with a value other than 7 will be set to NoData, and cells that are 7 will be set to value 1 on the output.

# Name: SetNull_Ex_02.py
# Description: Returns NoData if a conditional evaluation is 
#              true and returns the value specified by another
#              raster if it is false, on a cell-by-cell basis.
# 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 = "landclass"
inFalseRaster = 1
whereClause = "VALUE <> 7"

# Execute SetNull
outSetNull = SetNull(inRaster, inFalseRaster, whereClause)

# Save the output 
outSetNull.save("C:/sapyexamples/output/outsetnull")

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