GRASS GIS manual: v.random

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NAME

v.random - Randomly generate a 2D/3D vector points map.

KEYWORDS

vector, statistics

SYNOPSIS

v.random
v.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

BUGS

The RNG used by v.perturb should probably be added to this program.

AUTHOR

James Darrell McCauley <darrell@mccauley-usa.com>,
when he was at: Agricultural Engineering Purdue University

Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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