NAME

       r.random.cells  - Generates random cell values with spatial dependence.

KEYWORDS

       raster, sampling, random, autocorrelation

SYNOPSIS

       r.random.cells
       r.random.cells --help
       r.random.cells   output=name   distance=float    [seed=integer]    [--overwrite]   [--help]   [--verbose]
       [--quiet]  [--ui]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       output=name [required]
           Name for output raster map

       distance=float [required]
           Maximum distance of spatial correlation (value >= 0.0)

       seed=integer
           Random seed (SEED_MIN >= value >= SEED_MAX) (default [random])

DESCRIPTION

       r.random.cells generates a random sets of raster cells that are at least distance apart.  The  cells  are
       numbered from 1 to the numbers of cells generated, all other cells are 0 (zero). Random cells will not be
       generated in areas masked off.

   Detailed parameter description
       output
           Random cells. Each random cell has a unique non-zero cell value ranging from 1 to the number of cells
           generated.  The  heuristic  for  this  algorithm  is  to randomly pick cells until there are no cells
           outside of the chosen cell’s buffer of radius distance.

       distance
           Determines the minimum distance the centers of the random cells will be apart.

       seed
           Specifies the random seed that r.random.cells will use to generate the cells. If the random  seed  is
           not given, r.random.cells will get a seed from the process ID number.

NOTES

       The  original  purpose  for  this  program was to generate independent random samples of cells in a study
       area. The distance value is the amount of spatial autocorrelation for the map being studied.

EXAMPLE

       North Carolina sample dataset example:
       g.region n=228500 s=215000 w=630000 e=645000 res=100 -p
       r.random.cells output=random_500m distance=500
       # optionally set 0 to NULL (masked off areas)
       r.null random_500m setnull=0

REFERENCES

       Random Field Software for GRASS GIS by Chuck Ehlschlaeger

       As part of my dissertation, I put together several programs that help  GRASS  (4.1  and  beyond)  develop
       uncertainty  models of spatial data. I hope you find it useful and dependable. The following papers might
       clarify their use:

           •   Ehlschlaeger,  C.R.,  Shortridge,  A.M.,  Goodchild,  M.F.,  1997.   Visualizing   spatial   data
               uncertainty      using      animation.       Computers     &     Geosciences     23,     387-395.
               doi:10.1016/S0098-3004(97)00005-8

           •   Modeling Uncertainty in Elevation Data for Geographical Analysis, by Charles R. Ehlschlaeger, and
               Ashton M.  Shortridge. Proceedings of the 7th International Symposium on Spatial  Data  Handling,
               Delft, Netherlands, August 1996.

           •   Dealing  with  Uncertainty in Categorical Coverage Maps: Defining, Visualizing, and Managing Data
               Errors, by Charles Ehlschlaeger and  Michael  Goodchild.   Proceedings,  Workshop  on  Geographic
               Information  Systems  at the Conference on Information and Knowledge Management, Gaithersburg MD,
               1994.

           •   Uncertainty in Spatial  Data:  Defining,  Visualizing,  and  Managing  Data  Errors,  by  Charles
               Ehlschlaeger and Michael Goodchild. Proceedings, GIS/LIS’94, pp. 246-253, Phoenix AZ, 1994.

SEE ALSO

        r.random.surface, r.random

AUTHOR

       Charles  Ehlschlaeger; National Center for Geographic Information and Analysis, University of California,
       Santa Barbara.

       Last changed: $Date: 2015-04-21 16:00:05 +0200 (Tue, 21 Apr 2015) $

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       © 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual

GRASS 7.0.3                                                                               r.random.cells(1grass)