<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: v.perturb</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" href="grassdocs.css" type="text/css"> </head> <body bgcolor="white"> <img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade> <h2>NAME</h2> <em><b>v.perturb</b></em> - Random location perturbations of GRASS vector points <h2>KEYWORDS</h2> vector <h2>SYNOPSIS</h2> <b>v.perturb</b><br> <b>v.perturb help</b><br> <b>v.perturb</b> [-<b>q</b>] <b>input</b>=<em>name</em> <b>output</b>=<em>name</em> [<b>distribution</b>=<em>string</em>] <b>parameters</b>=<em>float</em>[,<i>float</i>,...] [<b>minimum</b>=<em>float</em>] [<b>seed</b>=<em>integer</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>-q</b></DT> <DD>Quiet</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>input</b>=<em>name</em></DT> <DD>Vector points to be spatially perturbed</DD> <DT><b>output</b>=<em>name</em></DT> <DD>Name for output vector map</DD> <DT><b>distribution</b>=<em>string</em></DT> <DD>Distribution of perturbation</DD> <DD>Options: <em>uniform,normal</em></DD> <DD>Default: <em>uniform</em></DD> <DT><b>parameters</b>=<em>float[,<i>float</i>,...]</em></DT> <DD>Parameter(s) of distribution. If the distribution is uniform, only one parameter, the maximum, is needed. For a normal distribution, two parameters, the mean and standard deviation, are required.</DD> <DT><b>minimum</b>=<em>float</em></DT> <DD>Minimum deviation in map units</DD> <DD>Default: <em>0.0</em></DD> <DT><b>seed</b>=<em>integer</em></DT> <DD>Seed for random number generation</DD> <DD>Default: <em>0</em></DD> </DL> <H2>DESCRIPTION</H2> <EM>v.perturb</EM> reads a vector map of points and writes the same points but <EM>perturbs</EM> the eastings and northings by adding either a uniform or normal delta value. Perturbation means that a variating spatial deviation is added to the coordinates. <H2>NOTES</H2> The uniform distribution is always centered about zero. The associated <em>parameter</em> is constrained to be positive and specifies the maximum of the distribution; the minimum is the negation of that parameter. Do perturb into a ring around the center, the <em>minimum</em> parameter can be used. <P> Usually, the mean (first parameter) of the normal distribution is zero (i.e., the distribution is centered at zero). The standard deviation (second parameter) is naturally constrained to be positive. <P> Output vector points are not guaranteed to be contained within the current geographic region. <H2>SEE ALSO</H2> <EM><A HREF="v.random.html">v.random</A></EM><br> <EM><A HREF="v.univar.html">v.univar</A></EM><br> <H2>AUTHOR</H2> <A HREF="http://mccauley-usa.com/">James Darrell McCauley</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> Random number generators originally written in FORTRAN by Wes Peterson and translated to C using <i>f2c</i>. <p><i>Last changed: $Date: 2006-03-03 11:41:45 +0100 (Fri, 03 Mar 2006) $</i> <HR> <P><a href="index.html">Main index</a> - <a href="vector.html">vector index</a> - <a href="full_index.html">Full index</a></P> <P>© 2003-2008 <a href="http://grass.osgeo.org">GRASS Development Team</a></p> </body> </html>
