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v.random.1grass
Langue: en
Version: 329590 (ubuntu - 24/10/10)
Section: 1 (Commandes utilisateur)
NAME
v.random - Randomly generate a 2D/3D vector points map.KEYWORDS
vector, statisticsSYNOPSIS
v.randomv.random help
v.random [-zdb] output=name n=integer [zmin=float] [zmax=float] [column=string] [--overwrite] [--verbose] [--quiet]
Flags:
- -z
Create 3D output- -d
Use drand48() function instead of rand()- -b
Do not build topology- --overwrite
Allow output files to overwrite existing files- --verbose
Verbose module output- --quiet
Quiet module output
Parameters:
- output=name
Name for output vector map- n=integer
Number of points to be created- zmin=float
Minimum z height (needs -z flag or column name)
Default: 0.0- zmax=float
Maximum z height (needs -z flag or column name)
Default: 0.0- column=string
Column name and type (i.e. INTEGER, DOUBLE PRECISION) for z values
If type is not given then DOUBLE PRECISION is used. Writes Z data to column instead of 3D vector.
DESCRIPTION
v.random randomly generates vector points within the current region using the selected random number generator.v.random can generate also 3D vector points or write random value to attribute table. Point height range or attribute value range is controlled by specifying zmin and zmax values. Both z values are included in range (zmin >= z <= zmax). Generated random attribute value type can be controlled by column data type. Use INTEGER column type for integers and DOUBLE PRECISION for floating point numbers. Integer values are calculated by rounding random floating point number.
EXAMPLES
Generate 20 random points with binary attribute (only 0 or 1):v.random output=binary_random n=20 zmin=0 zmax=1 column='binary INTEGER'
Get 20 random samples from raster map:
v.random output=random_samples n=20
v.db.addtable map=random_samples layer=1 columns='cat INTEGER, sample DOUBLE PRECISION'
v.what.rast vector=random_samples raster=elevation.10m@PERMANENT layer=1 column=sample
Generate 20 random points and sample attribute data from geology (vector) map:
v.random output=random_samples n=20
v.db.addtable map=random_samples layer=1 columns='cat integer, geology varchar(100)'
v.what.vect vector=random_samples layer=1 column=geology qvector=geology@PERMANENT qlayer=1 qcolumn=label
SEE ALSO
UNIX man pages for rand(3) and drand48(3).g.region, r.random, v.perturb, v.sample v.what.rast v.what.vect
BUGS
The RNG used by v.perturb should probably be added to this program.AUTHOR
James Darrell McCauley ,when he was at: Agricultural Engineering Purdue University
Last changed: $Date: 2008-08-03 20:28:11 +0200 (dom, 03 ago 2008) $
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