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

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)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual