v.net.components - Computes strongly and weakly connected
components in the network.
vector, network, components
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]
- -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
- 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
Last changed: $Date: 2017-11-02 11:53:40 +0100 (Thu, 02 Nov 2017) $
Available at: v.net.components source code (history)
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