1v.net.components(1)         GRASS GIS User's Manual        v.net.components(1)
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NAME

6       v.net.components   -  Computes strongly and weakly connected components
7       in the network.
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KEYWORDS

10       vector, network, components
11

SYNOPSIS

13       v.net.components
14       v.net.components --help
15       v.net.components       [-a]       input=name         [arc_layer=string]
16       [node_layer=string]     [arc_column=name]    [arc_backward_column=name]
17       [node_column=string]     output=name    method=string     [--overwrite]
18       [--help]  [--verbose]  [--quiet]  [--ui]
19
20   Flags:
21       -a
22           Add points on nodes
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24       --overwrite
25           Allow output files to overwrite existing files
26
27       --help
28           Print usage summary
29
30       --verbose
31           Verbose module output
32
33       --quiet
34           Quiet module output
35
36       --ui
37           Force launching GUI dialog
38
39   Parameters:
40       input=name [required]
41           Name of input vector map
42           Or data source for direct OGR access
43
44       arc_layer=string
45           Arc layer
46           Vector  features can have category values in different layers. This
47           number determines which layer to use. When used with direct OGR ac‐
48           cess this is the layer name.
49           Default: 1
50
51       node_layer=string
52           Node layer
53           Vector  features can have category values in different layers. This
54           number determines which layer to use. When used with direct OGR ac‐
55           cess this is the layer name.
56           Default: 2
57
58       arc_column=name
59           Arc forward/both direction(s) cost column (number)
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61       arc_backward_column=name
62           Arc backward direction cost column (number)
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64       node_column=string
65           Node cost column (number)
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67       output=name [required]
68           Name for output vector map
69
70       method=string [required]
71           Type of components
72           Options: weak, strong
73           weak: Weakly connected components
74           strong: Strongly connected components
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DESCRIPTION

77       v.net.components  computes the weakly and strongly connected components
78       in a network.
79

NOTES

81       Two nodes, u and v are in the  same  strongly  connected  component  if
82       there  are directed paths from u to v and from v to u. The nodes are in
83       the same weakly connected component if, ignoring edge directions, there
84       is a path between them.
85
86       The  type of components is specified by method parameter.  v.net.compo‐
87       nents creates a table and links it to layer 1. This table contains only
88       two  integer  columns:  cat and comp. If a point or both endpoints of a
89       line belong to the same component then the point/line is written to the
90       output  map  and  appropriate information is stored in the table. If -a
91       flag is set then new points are added  on  the  nodes  without  points.
92       These points have category numbers larger than any category used in the
93       input map.
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95       One-way roads can be defined by assigning a cost of -1 to the appropri‐
96       ate  cost column (arc_column or arc_backward_column). This affects only
97       strongly connected components. Network nodes can be closed by assigning
98       a cost of -1 to the node cost column. All nodes with a cost < 0 can not
99       be traversed and are end points, while all nodes with a cost ≥ 0  can
100       be  traversed.   This affects both weakly and strongly connected compo‐
101       nents.
102

EXAMPLES

104       Any road network should form a  single  strongly  connected  component.
105       Otherwise, it is impossible to travel between some places.
106       v.net.components input=roads output=roads_components method=strong
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SEE ALSO

109        v.net, v.category
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AUTHORS

112       Daniel Bundala, Google Summer of Code 2009, Student
113       Wolf Bergenheim, Mentor
114       Markus Metz
115

SOURCE CODE

117       Available at: v.net.components source code (history)
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119       Accessed: Saturday Oct 28 18:18:39 2023
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121       Main  index  | Vector index | Topics index | Keywords index | Graphical
122       index | Full index
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124       © 2003-2023 GRASS Development Team, GRASS GIS 8.3.1 Reference Manual
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128GRASS 8.3.1                                                v.net.components(1)
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