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.
-
The maximum length of the logical expression is 4,096 characters.
-
In Python, the {where_clause} should be enclosed in quotes, for example, "Value > 5".
Syntax
| Parameter | Explanation | Data Type |
in_conditional_raster |
Input raster representing the true or false result of the desired condition. | 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. Consult the documentation for more information on the SQL reference for query expressions used in ArcGIS and specifying a query in Python. | 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
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")
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
# Author: ESRI
# 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"
# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")
# Execute SetNull
outSetNull = SetNull(inRaster, inFalseRaster, whereClause)
# Save the output
outSetNull.save("C:/sapyexamples/output/outsetnull")