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## NAME

**r.random.cells** - Generates random cell values with spatial dependence.
## KEYWORDS

raster, random, cell
## SYNOPSIS

**r.random.cells**

**r.random.cells help**

**r.random.cells** **output**=*name* **distance**=*float* [**seed**=*integer*] [--**overwrite**] [--**verbose**] [--**quiet**]
### Flags:

**--overwrite**
- Allow output files to overwrite existing files
**--verbose**
- Verbose module output
**--quiet**
- Quiet module output

### Parameters:

**output**=*name*
- Name for output raster map
**distance**=*float*
- Maximum distance of spatial correlation (value(s) >= 0.0)
**seed**=*integer*
- Random seed (SEED_MIN >= value >= SEED_MAX) (default [random])

## DESCRIPTION

*r.random.cells* generates a random sets of cells that are at
least **distance** apart. The cells are numbered from 1 to the
numbers of cells generated. 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.
## REFERENCES

Random Field Software for GRASS 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: 2011-10-07 12:53:04 -0700 (Fri, 07 Oct 2011) $*

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