r.random.cells(1)

1r.random.cells(1)             Grass User's Manual            r.random.cells(1)
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NAME

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

9       raster
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SYNOPSIS

12       r.random.cells
13       r.random.cells help
14       r.random.cells  output=string distance=float  [seed=integer]   [--over‐
15       write]
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17   Flags:
18       --overwrite
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20   Parameters:
21       output=string
22           Name of indepent cells map
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24       distance=float
25           Input value: max. distance of spatial correlation (value(s) >= 0.0)
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27       seed=integer
28           Input value: random seed (SEED_MIN >= value >=  SEED_MAX),  default
29           [random]
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DESCRIPTION

32       r.random.cells  generates a random sets of cells that are at least dis‐
33       tance apart. The cells are numbered from 1 to the numbers of cells gen‐
34       erated. Random cells will not be generated in areas masked off.
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PARAMETERS

37       output   Output  map:  Random cells. Each random cell has a unique non-
38       zero cell value ranging from 1 to the number of  cells  generated.  The
39       heuristic  for this algorithm is to randomly pick cells until there are
40       no cells outside of the chosen cell's buffer of radius distance.
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42       distance Input value(s) [default 0.0]: distance determines the  minimum
43       distance the centers of the random cells will be apart.
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45       seed  Input  value  [default:  random]:  Specifies the random seed that
46       r.random.cells will use to generate the cells. If the  random  seed  is
47       not given, r.random.cells will get a seed from the process ID number.
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NOTES

50       The  original purpose for this program was to generate independent ran‐
51       dom samples of cells in a study area. The distance value is the  amount
52       of  spatial  autocorrelation  for  the map being studied. The amount of
53       spatial autocorrelation can be determined by using r.2Dcorrelogram with
54       r.2Dto1D, or r.1Dcorrelogram. With distance set to zero, the output map
55       will number each non-masked cell from 1 to  the  number  of  non-masked
56       cells in the study region.
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REFERENCES

59       Random Field Software for GRASS by Chuck Ehlschlaeger
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61       As  part  of my dissertation, I put together several programs that help
62       GRASS (4.1 and beyond) develop uncertainty models of  spatial  data.  I
63       hope  you  find  it  useful  and dependable. The following papers might
64       clarify their use:
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66       "Visualizing Spatial Data Uncertainty Using Animation  (final  draft),"
67       by Charles R.  Ehlschlaeger, Ashton M. Shortridge, and Michael F. Good‐
68       child. Submitted  to  Computers  in  GeoSciences  in  September,  1996,
69       accepted October, 1996 for publication in June, 1997.
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71       "Modeling  Uncertainty in Elevation Data for Geographical Analysis", by
72       Charles R. Ehlschlaeger, and Ashton M.  Shortridge. Proceedings of  the
73       7th  International  Symposium  on Spatial Data Handling, Delft, Nether‐
74       lands, August 1996.
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76       "Dealing with Uncertainty in Categorical Coverage Maps: Defining, Visu‐
77       alizing, and Managing Data Errors", by Charles Ehlschlaeger and Michael
78       Goodchild.  Proceedings, Workshop on Geographic Information Systems  at
79       the  Conference  on  Information and Knowledge Management, Gaithersburg
80       MD, 1994.
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82       "Uncertainty in Spatial Data: Defining, Visualizing, and Managing  Data
83       Errors",  by  Charles  Ehlschlaeger and Michael Goodchild. Proceedings,
84       GIS/LIS'94, pp. 246-253, Phoenix AZ, 1994.
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AUTHOR

92       Charles  Ehlschlaeger;  National  Center for Geographic Information and
93       Analysis, University of California, Santa Barbara.
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95       Last changed: $Date: 2006/04/20 21:31:23 $
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97       Full index
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101GRASS 6.2.2                                                  r.random.cells(1)