Lookup (Spatial Analyst)

Summary

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

Illustration

OutRas = Lookup(InRas1, "Category")

Usage

• Both numeric (integer or floating point) or string field types are supported. If the field is integer or string, the output will be an integer raster; otherwise, the output raster will be a floating-point raster.

• If the lookup field is of integer 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 string type, the lookup field will appear in the output raster attribute table, and the value field will be the same numeric type 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, consider the attribute table of an input raster with string field Text1

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

  The attribute table of the output raster from running Lookup on the Text1 field would be

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

• 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 that contains a field from which to create a new raster.	Raster Layer
Lookup field	Field containing the desired values for the new raster. It can be a numeric or string type.	Field

Return Value

Label	Explanation	Data Type
Output raster	The output raster whose values are determined by the specified field of the input raster.	Raster

Python

Lookup(in_raster, lookup_field)

Name	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 desired values for the new raster. It can be a numeric or string type.	Field

Return Value

Name	Explanation	Data Type
out_raster	The output raster whose values are determined by the specified field of the input 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

# 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"

# Execute Lookup
outRaster = Lookup(inRaster, lookupField)

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

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