Lookup (Spatial Analyst)

Summary

Creates a new raster by looking up values found in another field in the table of the input raster.

Usage

• If the lookup field is a numeric type, the values of that field will be written to the output raster attribute table as Value. Other items in the input raster attribute table will not be transferred to the output raster attribute table.

  For example, an attribute table of input raster with numeric field Attr1:

      Value   Count   Attr1
      1       294     1
      2       345     8
      3       654     3

  Output attribute table from Lookup on Attr1 field:

      Value   Count
      1       294
      3       654
      8       345

• If the lookup field is a character type, the lookup field will appear in the output raster attribute table, and the value field will be the same as for input raster. Any other items in the input raster's attribute table will not be transferred to the output raster's attribute table.

  For example, an attribute table of input raster with character field Text1:

      Value   Count   Attr1   Text1
      1        294    1       A
      2       6218    8       B
      3         28    3
      4       3603    9       3

  Output attribute table from Lookup on Text1 field:

      Value   Count   Text1
      1        294    A
      2       6218    B
      3         28    
      4       3603    3

Syntax

Lookup (in_raster, lookup_field)

Parameter	Explanation	Data Type
in_raster	The input raster that contains a field from which to create a new raster.	Raster Layer
lookup_field	Field containing the values for the new raster.	Field

Return Value

Name	Explanation	Data Type
out_raster	The output reclassified raster.	Raster

Code Sample

Lookup example 1 (Python window)

This example creates a new raster determined by the specified field of the input raster.

import arcpy
from arcpy import env  
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outRaster = Lookup("mycity","land_code")
outRaster.save("C:/sapyexamples/output/mylandcode.img")

Lookup example 2 (stand-alone script)

This example creates a new raster determined by the specified field of the input raster.

# Name: lookup_example02.py
# Description: Creates a new raster by looking up values found in another 
#              field in the table of the input raster.
# 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 = "mycity"
lookupField = "land_code"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Execute Lookup
outRaster = Lookup(inRaster, lookupField)

# Save the output 
outRaster.save("C:/sapyexamples/output/mylandcode")

Environments

Cell Size, Current Workspace, Mask, Output Coordinate System, Extent, Scratch Workspace, Snap Raster

Licensing Information

ArcView: Requires Spatial Analyst or 3D Analyst

ArcEditor: Requires Spatial Analyst or 3D Analyst

ArcInfo: Requires Spatial Analyst or 3D Analyst