1v.net.components(1) Grass User's Manual v.net.components(1)
2
6 v.net.components - Computes strongly and weakly connected components
7 in the network.
8
10 vector, network, components
11
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 Flags:
21 -a
22 Add points on nodes
23 --overwrite
25 Allow output files to overwrite existing files
26 --help
28 Print usage summary
29 --verbose
31 Verbose module output
32 --quiet
34 Quiet module output
35 --ui
37 Force launching GUI dialog
38 Parameters:
40 input=name [required]
41 Name of input vector map
42 Or data source for direct OGR access
43 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
48 access this is the layer name.
49 Default: 1
50 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
55 access this is the layer name.
56 Default: 2
57 arc_column=name
59 Arc forward/both direction(s) cost column (number)
60 arc_backward_column=name
62 Arc backward direction cost column (number)
63 node_column=string
65 Node cost column (number)
66 output=name [required]
68 Name for output vector map
69 method=string [required]
71 Type of components
72 Options: weak, strong
73 weak: Weakly connected components
74 strong: Strongly connected components
75
77 v.net.components computes the weakly and strongly connected components
78 in a network.
79
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 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.
94 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
100 can be traversed. This affects both weakly and strongly connected com‐
101 ponents.
102
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
107
109 v.net, v.category,
110
112 Daniel Bundala, Google Summer of Code 2009, Student
113 Wolf Bergenheim, Mentor
114 Markus Metz
115 Last changed: $Date: 2017-11-02 11:53:40 +0100 (Thu, 02 Nov 2017) $
117
119 Available at: v.net.components source code (history)
120 Main index | Vector index | Topics index | Keywords index | Graphical
122 index | Full index
123 © 2003-2019 GRASS Development Team, GRASS GIS 7.6.0 Reference Manual
125GRASS 7.6.0 v.net.components(1)