## NAME

**v.perturb** - Random location perturbations of GRASS vector points
## KEYWORDS

vector
## SYNOPSIS

**v.perturb**

**v.perturb help**

**v.perturb** [-**q**] **input**=*name* **output**=*name* [**distribution**=*string*] **parameters**=*float*[,*float*,...] [**minimum**=*float*] [**seed**=*integer*] [--**overwrite**] [--**verbose**] [--**quiet**]
### Flags:

**-q**
- Quiet
**--overwrite**
- Allow output files to overwrite existing files
**--verbose**
- Verbose module output
**--quiet**
- Quiet module output

### Parameters:

**input**=*name*
- Vector points to be spatially perturbed
**output**=*name*
- Name for output vector map
**distribution**=*string*
- Distribution of perturbation
- Options:
*uniform,normal*
- Default:
*uniform*
**parameters**=*float[,**float*,...]
- 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 normal 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
current geographic region.

## 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*.

*Last changed: $Date: 2006-03-03 02:41:45 -0800 (Fri, 03 Mar 2006) $*

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