Weighted Sum (Spatial Analyst)
Summary
Overlays several rasters, multiplying each by their given weight and summing them together.
Illustration
Usage
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A useful way to add several rasters together is to input multiple rasters and set all weights equal to 1.
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Input rasters can be integer or floating point.
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The weight values can be any positive or negative decimal value. It is not restricted to a relative percentage or equal to 1.0.
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The weight will be applied to the specified field for the input raster. Fields can be of type short or long integer, double or float.
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By default, this tool will take advantage of multi-core processors. The maximum number of cores that can be utilized is limited to 4.
If you wish the tool to use fewer cores, use the parallelProcessingFactor environment setting.
Syntax
| Parameter | Explanation | Data Type |
in_rasters in_weighted_sum_table |
The Weighted Sum tool overlays several rasters, multiplying each by their given weight and summing them together. An Overlay class is used to define the table. The WSTable object is used to specify a Python list of input rasters and weight them accordingly. The form of the WSTable object is:
| WSTable |
Return Value
| Name | Explanation | Data Type |
| out_raster |
The output suitability raster. It will be of floating point type. | Raster |
Code Sample
This example creates a suitability raster for locating a ski resort by combining multiple rasters together, and applying appropriate weight factors.
import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
# Execute WeightedSum
outWeightedSum = WeightedSum(WSTable([["snow", "VALUE", 0.25], ["land", "VALUE",0.25],
["soil", "VALUE", 0.5]]))
outWeightedSum.save("C:/sapyexamples/output/outwsum")
This example creates a suitability raster for locating a ski resort by combining multiple rasters together, and applying appropriate weight factors.
# Name: WeightedSum_Ex_02.py
# Description: Overlays several rasters multiplying each by their given
# weight and summing them together.
# 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
inRaster1 = "snow"
inRaster2 = "land"
inRaster3 = "soil"
WSumTableObj = WSTable([[inRaster1, "VALUE", 0.25], [inRaster2, "VALUE", 0.25],
[inRaster3, "VALUE", 0.5]])
# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")
# Execute WeightedSum
outWeightedSum = WeightedSum(WSumTableObj)
# Save the output
outWeightedSum.save("C:/sapyexamples/output/weightsumout")