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