.TH r.random.cells 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBr.random.cells\fR\fR  - Generates random cell values with spatial dependence.
.SH KEYWORDS
raster, random, cell
.SH SYNOPSIS
\fBr.random.cells\fR
.br
\fBr.random.cells help\fR
.br
\fBr.random.cells output\fR=\fIname\fR \fBdistance\fR=\fIfloat\fR  [\fBseed\fR=\fIinteger\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBoutput\fR=\fIname\fR" 4m
.br
Name for output raster map
.IP "\fBdistance\fR=\fIfloat\fR" 4m
.br
Maximum distance of spatial correlation (value(s) >= 0.0)
.IP "\fBseed\fR=\fIinteger\fR" 4m
.br
Random seed (SEED_MIN >= value >= SEED_MAX) (default [random])
.PP
.SH DESCRIPTION
\fIr.random.cells\fR generates a random sets of cells that are at
least \fBdistance\fR apart. The cells are numbered from 1 to the
numbers of cells generated. Random cells will not be generated in
areas masked off.
.SS Detailed parameter description
.IP "\fBoutput\fR" 4m
.br
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 \fBdistance\fR.
.IP "\fBdistance\fR" 4m
.br
Determines the minimum distance the centers of the random cells
will be apart.
.IP "\fBseed\fR" 4m
.br
Specifies the random seed that
\fIr.random.cells\fR will use to generate the cells. If the random seed
is not given,\fI r.random.cells\fR will get a seed from the process ID
number.
.PP
.SH NOTES
The original purpose for this program was to generate independent
random samples of cells in a study area. The \fBdistance\fR value is
the amount of spatial autocorrelation for the map being studied. 
.SH REFERENCES
Random Field Software for GRASS by Chuck Ehlschlaeger
.PP
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:
.RS
.IP
 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
.IP
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.
.IP
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.
.IP
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.
.RE
.SH SEE ALSO
\fI
r.random.surface,
r.random
\fR 
.SH AUTHOR
Charles Ehlschlaeger; National Center for Geographic Information and
Analysis, University of California, Santa Barbara.
.PP
\fILast changed: $Date: 2011-10-07 21:53:04 +0200 (Fri, 07 Oct 2011) $\fR
.PP
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.PP
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