table of contents
v.net.components(1grass) | GRASS GIS User's Manual | v.net.components(1grass) |
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:¶
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
DESCRIPTION¶
v.net.components computes the weakly and strongly connected components in a network.
NOTES¶
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.
EXAMPLES¶
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
SEE ALSO¶
v.net, v.category
AUTHORS¶
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
Markus Metz
SOURCE CODE¶
Available at: v.net.components source code (history)
Accessed: Saturday Jul 27 17:08:47 2024
Main index | Vector index | Topics index | Keywords index | Graphical index | Full index
© 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual
GRASS 8.4.0 |