v.perturb(1grass)

1v.perturb(1)                  Grass User's Manual                 v.perturb(1)
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NAME

6       v.perturb  - Random location perturbations of vector points.
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KEYWORDS

9       vector, geometry, statistics, random, point pattern, level1
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SYNOPSIS

12       v.perturb
13       v.perturb --help
14       v.perturb  [-b]  input=name   [layer=string]   output=name   [distribu‐
15       tion=string]        parameters=float[,float,...]        [minimum=float]
16       [seed=integer]     [--overwrite]    [--help]    [--verbose]   [--quiet]
17       [--ui]
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19   Flags:
20       -b
21           Do not build topology
22           Advantageous when handling a large number of points
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24       --overwrite
25           Allow output files to overwrite existing files
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27       --help
28           Print usage summary
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30       --verbose
31           Verbose module output
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33       --quiet
34           Quiet module output
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36       --ui
37           Force launching GUI dialog
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39   Parameters:
40       input=name [required]
41           Name of input vector map
42           Or data source for direct OGR access
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44       layer=string
45           Layer number or name (’-1’ for all layers)
46           A single vector map can be connected to multiple  database  tables.
47           This  number  determines  which table to use. When used with direct
48           OGR access this is the layer name.
49           Default: -1
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51       output=name [required]
52           Name for output vector map
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54       distribution=string
55           Distribution of perturbation
56           Options: uniform, normal
57           Default: uniform
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59       parameters=float[,float,...] [required]
60           Parameter(s) of distribution
61           If the distribution is uniform, only one parameter, the maximum, is
62           needed.  For  a  normal  distribution, two parameters, the mean and
63           standard deviation, are required.
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65       minimum=float
66           Minimum deviation in map units
67           Default: 0.0
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69       seed=integer
70           Seed for random number generation
71           Default: 0
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DESCRIPTION

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

80       The uniform distribution is always centered about zero.  The associated
81       parameter is constrained to be positive and specifies  the  maximum  of
82       the  distribution;  the  minimum  is the negation of that parameter. Do
83       perturb into a ring around the center, the  minimum  parameter  can  be
84       used.
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86       Usually,  the mean (first parameter) of the normal distribution is zero
87       (i.e., the distribution is centered at zero).  The  standard  deviation
88       (second parameter) is naturally constrained to be positive.
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90       Output vector points are not guaranteed to be contained within the cur‐
91       rent geographic region.
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EXAMPLES

94   Random, uniformly distributed selection
95       To create a random, uniformly distributed  selection  of  possible  new
96       points with a radius of 100,000 map units, use the following command:
97       v.perturb input=comm_colleges output=uniform_perturb parameters=100000
98       Your map should look similar to this figure:
99       Figure:  Map  showing the actual community college points and uniformly
100       random chosen points.
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102   Normal distributed selection
103       For a normal distribution with a mean of 5000 and standard deviation of
104       2000, use the following command:
105       v.perturb input=comm_colleges output=normal_perturb distribution=normal parameters=5000,2000
106       Figure:  Map  showing  the actual community college points and normally
107       random chosen and colored points. Notice that each point is  closer  to
108       the original point.
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110   Normal distributed selection with a minimum value
111       In order to include a minimum value of 500, use the following command:
112       v.perturb input=comm_colleges output=min_perturb distribution=normal parameters=100000,1000 minimum=500
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AUTHOR

118       James Darrell McCauley
119       when he was at: Agricultural Engineering Purdue University
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121       Random  number generators originally written in FORTRAN by Wes Peterson
122       and translated to C using f2c.
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124       Last changed: $Date: 2018-01-07 16:12:07 +0100 (Sun, 07 Jan 2018) $
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SOURCE CODE

127       Available at: v.perturb source code (history)
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129       Main index | Vector index | Topics index | Keywords index  |  Graphical
130       index | Full index
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132       © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
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136GRASS 7.4.4                                                       v.perturb(1)