Aggregate (Spatial Analyst)

Available with Spatial Analyst license.

Summary

Generates a reduced-resolution version of a raster. Each output cell contains the Sum, Minimum, Maximum, Mean, or Median of the input cells that are encompassed by the extent of that cell.

Learn more about how Aggregate works

Illustration

OutRas = Aggregate(InRas1, 3, Max, Expand, Data)

Usage

• For the Aggregation technique settings of Maximum, Minimum, or Sum, the output raster type will be the same as that of the input raster. If the setting is Mean or Median, the output type will always be float.

• The geoprocessing analysis environments Extent and Cell size are recognized by this tool. To determine the output raster's resolution when an integer cell size has been specified, multiply the cell resolution of the analysis environment by the input cell factor parameter. If the cell size for the analysis environment is set to the minimum or maximum of the inputs, the resolution of the output raster will be the product of the input raster's resolution multiplied by the specified cell factor.

• 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 to be aggregated. It can be of integer or floating point type.	Raster Layer
Cell factor	The factor by which the cell size of the input raster will be multiplied. The value must be an integer greater than 1. For example, a cell factor value of 3 results in an output cell size three times larger than that of the input raster.	Long
Aggregation technique (Optional)	The method that will be used for aggregation. The values of the input cells encompassed by the coarser output cells are aggregated by one of the following statistics: Sum—The total of the input cell values. This is the default. Maximum—The largest value of the input cells. Mean—The average value of the input cells. Median—The median value of the input cells. Minimum—The smallest value of the input cells.	String
Expand extent if needed (Optional)	Specifies whether the boundaries of the input raster will be expanded when its rows or columns are not a multiple of the cell factor. Checked—The top or right boundaries of the input raster will be expanded so the total number of cells in a row or column is a multiple of the cell factor. Those expanded cells are given a value of NoData when put into the calculation. With this option, the output raster can cover a larger spatial extent than the input raster. This is the default. Unchecked—The number of rows or columns will be reduced in the output raster. This truncates the remaining cells on the top or right boundaries of the input raster, making the number of rows or columns in the input raster a multiple of the cell factor. With this option, the output raster can cover a smaller spatial extent than the input raster. If the number of rows and columns in the input raster is a multiple of the Cell factor, these keywords are not used.	Boolean
Ignore NoData in calculations (Optional)	Specifies whether NoData valueswill be ignored during the aggregation calculation. Checked—Specifies that if NoData values exist for any of the cells that fall within the spatial extent of a larger cell on the output raster, the NoData values will be ignored when determining the value for output cell locations. Only input cells within the extent of the output cell that have data values will be used in determining the value of the output cell. This is the default. Unchecked—Specifies that if any cell that falls within the spatial extent of a larger cell on the output raster has a value of NoData, the value for that output cell location will be NoData. When this option is used, it is implied that when cells within an aggregation contain the NoData value, there is insufficient information to perform the specified calculations necessary to determine an output value.	Boolean

Return Value

Label	Explanation	Data Type
Output raster	The output aggregated raster. It is a reduced-resolution version of the input raster.	Raster

Python

Aggregate(in_raster, cell_factor, {aggregation_type}, {extent_handling}, {ignore_nodata})

Name	Explanation	Data Type
in_raster	The input raster to be aggregated. It can be of integer or floating point type.	Raster Layer
cell_factor	The factor by which the cell size of the input raster will be multiplied. The value must be an integer greater than 1. For example, a cell factor value of 3 results in an output cell size three times larger than that of the input raster.	Long
aggregation_type (Optional)	The method that will be used for aggregation. The values of the input cells encompassed by the coarser output cells are aggregated by one of the following statistics: SUM—The total of the input cell values. This is the default. MAXIMUM—The largest value of the input cells. MEAN—The average value of the input cells. MEDIAN—The median value of the input cells. MINIMUM—The smallest value of the input cells.	String
extent_handling (Optional)	Specifies whether the boundaries of the input raster will be expanded when its rows or columns are not a multiple of the cell factor. EXPAND—The top or right boundaries of the input raster will be expanded so the total number of cells in a row or column is a multiple of the cell factor. Those expanded cells are given a value of NoData when put into the calculation.With this option, the output raster can cover a larger spatial extent than the input raster. This is the default. TRUNCATE—The number of rows or columns will be reduced by 1 in the output raster. This truncates the remaining cells on the top or right boundaries of the input raster, making the number of rows or columns in the input raster a multiple of the cell factor.With this option, the output raster can cover a smaller spatial extent than the input raster. If the number of rows and columns in the input raster is a multiple of the cell_factor, these keywords are not used.	Boolean
ignore_nodata (Optional)	Denotes whether NoData values are ignored by the aggregation calculation. DATA—Specifies that if NoData values exist for any of the cells that fall within the spatial extent of a larger cell on the output raster, the NoData values will be ignored when determining the value for output cell locations. Only input cells within the extent of the output cell that have data values will be used in determining the value of the output cell.This is the default. NODATA—Specifies that if any cell that falls within the spatial extent of a larger cell on the output raster has a value of NoData, the value for that output cell location will be NoData.When this option is used, it is implied that when cells within an aggregation contain the NoData value, there is insufficient information to perform the specified calculations necessary to determine an output value.	Boolean

Return Value

Name	Explanation	Data Type
out_raster	The output aggregated raster. It is a reduced-resolution version of the input raster.	Raster

Code sample

Aggregate example 1 (Python window)

This example aggregates a raster by averaging the values with a cell factor of 3 and outputs a TIFF raster.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outAggreg = Aggregate("highres", 3, "MAXIMUM", "TRUNCATE", "DATA")
outAggreg.save("C:/sapyexamples/output/aggregate.tif")

Aggregate example 2 (stand-alone script)

This example aggregates a raster by averaging the values with a cell factor of 3 and outputs a Grid raster.

# Name: Aggregate_Ex_02.py
# Description: Generates a reduced resolution version of a 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 = "highres"
cellFactor = 3

# Execute Aggregate
outAggreg = Aggregate(inRaster, cellFactor, "MEAN", "TRUNCATE", "NODATA")

# Save the output 
outAggreg.save("C:/sapyexamples/output/aggregate02")

Environments

Auto Commit, Cell Size, Cell Size Projection Method, Compression, Current Workspace, Extent, Geographic Transformations, Mask, Output CONFIG Keyword, Output Coordinate System, Parallel Processing Factor, Scratch Workspace, Snap Raster, Tile Size