Create Random Raster (Data Management)

Summary

Creates a random raster dataset based on a user-specified distribution and extent.

Usage

• The values assigned to each cell in the output raster are derived from the random number generator and the selected distribution type. There are several random number generators available for use, and the one you wish to use is identified in the Environments Settings, in the Random Numbers section. The random number generator starts a stream of random numbers based on the generator type and a seed value. These numbers are randomly determined and the values fall between 0 and 1. Each value is independent of the other values.

  Multiple distribution types are available for the random number generators when assigning (or transforming) the values in the output raster. The distributions generally produce different results, and which distribution to select is determined by the end use of the raster. If the random raster is to model some natural phenomenon, the distribution selected should be the best representation of the process of the phenomenon.

  For a description of the distributions and how they are generally used, see Distributions for assigning random values.

• The Uniform, Integer, Normal, and Exponential distributions' processing times are independent of their arguments, while the Poisson, Gamma, Binomial, Geometric, and Pascal distributions' processing times can vary considerably when arguments are changed.

• A default value is calculated for the cell size parameter if no value is provided. This value is based on the size of the extent.

Syntax

CreateRandomRaster_management (out_path, out_name, {distribution}, {raster_extent}, {cellsize})

Parameter	Explanation	Data Type
out_path	The location of the output raster dataset.	Workspace;Raster Catalog
out_name	The name of the raster dataset to be created. When not saving to a geodatabase, specify .tif for a TIFF file format, .img for an ERDAS IMAGINE file format, or no extension for a GRID file format.	String
distribution (Optional)	The distribution of random values desired is as follows: UNIFORM {Minimum}, {Maximum}—A uniform distribution with a range defined by the {Minimum} and {Maximum}. Both the {Minimum} and {Maximum} are of type double. The default values are 0.0 for {Minimum} and 1.0 for {Maximum}. INTEGER {Minimum}, {Maximum}—An integer distribution with a range defined by the {Minimum} and {Maximum}. Both the {Minimum} and {Maximum} are of type long. The default values are 1 for {Minimum} and 10 for {Maximum}. NORMAL {Mean}, {Standard Deviation}—A normal distribution with a defined {Mean} and {Standard Deviation}. Both the {Mean} and {Standard Deviation} are of type double. The default values are 0.0 for {Mean} and 1.0 for {Standard Deviation}. EXPONENTIAL {Mean}—An exponential distribution with a defined {Mean}. The {Mean} is of type double. The default value for {Mean} is 1.0. POISSON {Mean}—A Poisson distribution with a defined {Mean}. The {Mean} is of type double. The default value for {Mean} is 1.0. GAMMA {Alpha}, {Beta}—A gamma distribution with a defined {Alpha} and {Beta}. Both the {Alpha} and {Beta} are of type double. The default values are 1.0 for {Alpha} and 1.0 for {Beta}. BINOMIAL {N}, {Probability}—A binomial distribution with a defined {N} and {Probability}. The {N} is of type long and {Probability} is of type double. The default values are 10 for {N} and 0.5 for {Probability}. GEOMETRIC {Probability}—A geometric distribution with a defined {Probability}. The {Probability} is of type double. The default value for {Probability} is 0.5. NEGATIVE BINOMIAL {r}, {Probability}—A Pascal distribution with a defined {r} and {Probability}. The {r} is of type double and {Probability} is of type double. The default values are 10.0 for {r} and 0.5 for {Probability}.	String
raster_extent (Optional)	The spatial extent of the random raster dataset.	Extent
cellsize (Optional)	The cell size of the new random raster dataset.	Double

Code Sample

CreateRandomRaster example 1 (Python window)

This sample creates an output raster of random values with a normal distribution at the defined extent and cell size

import arcpy
arcpy.CreateRandomRaster_management("c:/output", "randrast", 
                                    "NORMAL 3.0", "0 0 500 500", 50)

CreateRandomRaster example 2 (stand-alone script)

This sample creates an output raster of random values with a Poisson distribution at the defined extent and cell size.

# Name: CreateRandomRaster_Ex_02.py
# Description: Creates a random raster dataset based on a 
#              user-specified distribution and extent.
# Requirements: None

# Import system modules
import arcpy

# Set local variables
outPath = "c:/output"
outFile = "randrast02"
distribution = "POISSON 6.4"
outExtent = "250 250 750 750"
cellSize = 25

# Execute CreateRandomRaster
arcpy.CreateRandomRaster_management(outPath, outFile, distribution, 
                                    outExtent, cellSize)

Environments

Compression, Current Workspace, Output CONFIG Keyword, Output XY Domain, Output Z Domain, Output Coordinate System, Extent, Output has Z values, Output Spatial Grid 1, 2, 3, Pyramid, Raster Statistics, Scratch Workspace, Tile Size, Z Resolution

Licensing Information

ArcGIS for Desktop Basic: Requires 3D Analyst or Spatial Analyst

ArcGIS for Desktop Standard: Requires 3D Analyst or Spatial Analyst

ArcGIS for Desktop Advanced: Yes