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 orientation of the
edges, 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 the given
layer.
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.
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
Last changed: $Date: 2013-05-23 21:59:24 +0200 (Thu, 23 May 2013) $
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GRASS Development Team,
GRASS GIS 7.0.3 Reference Manual