NAME
v.net.components - Computes strongly and weakly connected components in the network.
KEYWORDS
vector,
network,
components
SYNOPSIS
v.net.components
v.net.components --help
v.net.components [-a] input=name [arc_layer=string] [node_layer=string] [arc_column=name] [arc_backward_column=name] [node_column=string] output=name method=string [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -a
- Add points on nodes
- --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=name [required]
- Name of input vector map
- Or data source for direct OGR access
- arc_layer=string
- Arc layer
- Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
- Default: 1
- node_layer=string
- Node layer
- Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
- Default: 2
- arc_column=name
- Arc forward/both direction(s) cost column (number)
- arc_backward_column=name
- Arc backward direction cost column (number)
- node_column=string
- Node cost column (number)
- output=name [required]
- Name for output vector map
- method=string [required]
- Type of components
- Options: weak, strong
- weak: Weakly connected components
- strong: Strongly connected components
v.net.components computes the weakly and strongly connected
components in a network.
Two nodes,
u and
v are in the same strongly connected
component if there are directed paths from
u to
v and
from
v to
u. The nodes are in the same weakly
connected component if, ignoring edge directions, there is a path
between them.
The type of components is specified by method parameter.
v.net.components creates a table and links it to layer 1. This
table contains only two integer columns: cat and
comp. If a point or both endpoints of a line belong to the
same component then the point/line is written to the output map and
appropriate information is stored in the table. If -a flag is
set then new points are added on the nodes without points. These points
have category numbers larger than any category used in the input map.
One-way roads can be defined by assigning a cost of -1 to the
appropriate cost column (arc_column or
arc_backward_column). This affects only strongly connected
components. Network nodes can be closed by assigning a cost of -1 to
the node cost column. All nodes with a cost < 0 can not be traversed
and are end points, while all nodes with a cost ≥ 0 can be traversed.
This affects both weakly and strongly connected components.
Any road network should form a single strongly connected component.
Otherwise, it is impossible to travel between some places.
v.net.components input=roads output=roads_components method=strong
v.net,
v.category
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
Markus Metz
SOURCE CODE
Available at:
v.net.components source code
(history)
Latest change: Thursday Jan 26 14:10:26 2023 in commit: cdd84c130cea04b204479e2efdc75c742efc4843
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GRASS Development Team,
GRASS GIS 8.4.1dev Reference Manual