## NAME

v.net.spanningtree - Computes minimum spanning tree for the network.

## KEYWORDS

vector, network, spanning tree

## SYNOPSIS

v.net.spanningtree
v.net.spanningtree --help
v.net.spanningtree [-g] input=name output=name [arc_layer=string] [node_layer=string] [arc_column=name] [node_column=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

### Flags:

-g
  Use geodesic calculation for longitude-latitude locations
--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
output=name [required]
  Name for output vector map
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)
node_column=name
  Node cost column (number)

## DESCRIPTION

v.net.spanningtree finds the minimum spanning tree in a network.

## NOTES

A spanning tree is a minimum cost subnetwork connecting all nodes in an undirected network (same forward and backward costs). If a network is disconnected then the module computes the minimum spanning tree for each (weakly) connected component. So, strictly speaking, v.net.spanningtree does not compute spanning tree but a spanning forest. As the name suggests, a spanning tree is a tree. That is, it contains no cycles and if a component has N nodes then the tree has N-1 edges connecting all nodes. Accol is used to specify the costs of the edges. The output consists of the edges in the spanning tree.

## EXAMPLES

Find cheapest set of pipelines connecting all nodes.

    v.net.spanningtree input=projected_pipelines output=spanningtree accol=cost

## SEE ALSO

v.net, v.net.steiner

## AUTHORS

Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor

Last changed: $Date$

## SOURCE CODE

Available at: v.net.spanningtree source code (history)

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