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<title>GRASS GIS manual: v.random</title>
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<h2>NAME</h2>
<em><b>v.random</b></em> - Randomly generate a 2D/3D vector points map.
<h2>KEYWORDS</h2>
vector, statistics
<h2>SYNOPSIS</h2>
<b>v.random</b><br>
<b>v.random help</b><br>
<b>v.random</b> [-<b>zdb</b>] <b>output</b>=<em>name</em> <b>n</b>=<em>integer</em> [<b>zmin</b>=<em>float</em>] [<b>zmax</b>=<em>float</em>] [<b>column</b>=<em>string</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>]
<h3>Flags:</h3>
<DL>
<DT><b>-z</b></DT>
<DD>Create 3D output</DD>
<DT><b>-d</b></DT>
<DD>Use drand48() function instead of rand()</DD>
<DT><b>-b</b></DT>
<DD>Do not build topology</DD>
<DT><b>--overwrite</b></DT>
<DD>Allow output files to overwrite existing files</DD>
<DT><b>--verbose</b></DT>
<DD>Verbose module output</DD>
<DT><b>--quiet</b></DT>
<DD>Quiet module output</DD>
</DL>
<h3>Parameters:</h3>
<DL>
<DT><b>output</b>=<em>name</em></DT>
<DD>Name for output vector map</DD>
<DT><b>n</b>=<em>integer</em></DT>
<DD>Number of points to be created</DD>
<DT><b>zmin</b>=<em>float</em></DT>
<DD>Minimum z height (needs -z flag or column name)</DD>
<DD>Default: <em>0.0</em></DD>
<DT><b>zmax</b>=<em>float</em></DT>
<DD>Maximum z height (needs -z flag or column name)</DD>
<DD>Default: <em>0.0</em></DD>
<DT><b>column</b>=<em>string</em></DT>
<DD>Column name and type (i.e. INTEGER, DOUBLE PRECISION) for z values</DD>
<DD>If type is not given then DOUBLE PRECISION is used. Writes Z data to column instead of 3D vector.</DD>
</DL>
<h2>DESCRIPTION</h2>
<em>v.random</em> randomly generates vector points within the
current region using the selected random number generator.
<p><em>v.random</em> 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 (<em>zmin >= z <= zmax</em>).
Generated random attribute value type can be controlled by column
data type. Use <b>INTEGER</b> column type for integers and
<b>DOUBLE PRECISION</b> for floating point numbers. Integer values are
calculated by rounding random floating point number.
<h2>EXAMPLES</h2>
Generate 20 random points with binary attribute (only 0 or 1):
<div class="code"><pre>
v.random output=binary_random n=20 zmin=0 zmax=1 column='binary INTEGER'
</pre></div>
Get 20 random samples from raster map:
<div class="code"><pre>
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
</pre></div>
Generate 20 random points and sample attribute data from geology (vector) map:
<div class="code"><pre>
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
</pre></div>
<h2>SEE ALSO</h2>
UNIX man pages for <em>rand(3)</em> and <em>drand48(3)</em>.
<p>
<em>
<a href="g.region.html">g.region</a>,
<a href="r.random.html">r.random</a>,
<a href="v.perturb.html">v.perturb</a>,
<a href="v.sample.html">v.sample</a>
<a href="v.what.rast.html">v.what.rast</a>
<a href="v.what.vect.html">v.what.vect</a>
</em>
<h2>BUGS</h2>
The RNG used by
<em><a href="v.perturb.html">v.perturb</a></em>
should probably be added to this program.<br>
<h2>AUTHOR</h2>
<a href="http://mccauley-usa.com/">James Darrell McCauley</a>
<a href="mailto:darrell@mccauley-usa.com"><darrell@mccauley-usa.com></a>,
<br>when he was at:
<a href="http://ABE.www.ecn.purdue.edu/ABE/">Agricultural
Engineering</a>
<a href="http://www.purdue.edu/">Purdue University</a>
<p><i>Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $</i>
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