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v.perturb(1)		    GRASS GIS User's Manual		  v.perturb(1)

NAME
       v.perturb  - Random location perturbations of vector points.

KEYWORDS
       vector, geometry, statistics, random, point pattern, level1

SYNOPSIS
       v.perturb
       v.perturb --help
       v.perturb  [-b]	input=name   [layer=string]   output=name   [distribu-
       tion=string]  parameters=float[,float,...]  [minimum=float]   [seed=in-
       teger]	[--overwrite]  [--help]	 [--verbose]  [--quiet]	 [--ui]

   Flags:
       -b
	   Do not build	topology
	   Advantageous	when handling a	large number of	points

       --overwrite
	   Allow output	files to overwrite existing files

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       input=nameA [required]
	   Name	of input vector	map
	   Or data source for direct OGR access

       layer=string
	   Layer number	or name	('-1' for all layers)
	   A  single  vector map can be	connected to multiple database tables.
	   This	number determines which	table to use. When  used  with	direct
	   OGR access this is the layer	name.
	   Default: -1

       output=nameA [required]
	   Name	for output vector map

       distribution=string
	   Distribution	of perturbation
	   Options: uniform, normal
	   Default: uniform

       parameters=float[,float,...]A [required]
	   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.

       minimum=float
	   Minimum deviation in	map units
	   Default: 0.0

       seed=integer
	   Seed	for random number generation
	   Default: 0

DESCRIPTION
       v.perturb  reads	 a vector map of points	and writes the same points but
       perturbs	the eastings and northings by adding either a uniform or  nor-
       mal  delta value. Perturbation means that a variating spatial deviation
       is added	to the coordinates.

NOTES
       The uniform distribution	is always centered about zero.	The associated
       parameter  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 minimum parameter	can be
       used.

       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.

       Output vector points are	not guaranteed to be contained within the cur-
       rent geographic region.

EXAMPLES
   Random, uniformly distributed selection
       To  create  a  random,  uniformly distributed selection of possible new
       points with a radius of 100,000 map units, use the following command:
       v.perturb input=comm_colleges output=uniform_perturb parameters=100000
       Your map	should look similar to this figure:
       Figure: Map showing the actual community	college	points	and  uniformly
       random chosen points.

   Normal distributed selection
       For a normal distribution with a	mean of	5000 and standard deviation of
       2000, use the following command:
       v.perturb input=comm_colleges output=normal_perturb distribution=normal parameters=5000,2000
       Figure: Map showing the actual community	college	 points	 and  normally
       random  chosen  and colored points. Notice that each point is closer to
       the original point.

   Normal distributed selection	with a minimum value
       In order	to include a minimum value of 500, use the following command:
       v.perturb input=comm_colleges output=min_perturb	distribution=normal parameters=100000,1000 minimum=500

SEE ALSO
	v.random, v.univar

AUTHOR
       James Darrell McCauley
       when he was at: Agricultural Engineering	Purdue University

       Random number generators	originally written in FORTRAN by Wes  Peterson
       and translated to C using f2c.

SOURCE CODE
       Available at: v.perturb source code (history)

       Main  index  | Vector index | Topics index | Keywords index | Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.4 Reference	Manual

GRASS 7.8.4							  v.perturb(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHOR | SOURCE CODE

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