## DESCRIPTION

v.net.allpairs computes the shortest path between each selected node and all other selected nodes. The output is a vector with the selected nodes and the shortest paths.

## NOTES

An attribute table is created and linked to layer arc_layer. The table contains four columns: cat, from_cat, to_cat, cost. Each cat entry denotes the category of the shortest path from the node with category from_cat to the node with category to_cat. If points are specified by cats, layer or where parameters then the table is filled only for the selected points.
If arc_backward_column is not given then then the same costs are used for forward and backward arcs.

## EXAMPLE

Find shortest path along roads from selected archsites (Spearfish sample dataset):

    # prepare network: connect archsites to roads with threshold 200
    v.net input=roads@PERMANENT points=archsites@PERMANENT \
    output=roads_net operation=connect thresh=200

    # verify result
    v.category input=roads_net option=report

    # only lines should have a category in layer 1
    # only points should have a category in layer 2

    # shortest path between all points with categories 1 - 5 in layer 2
    v.net.allpairs input=roads_net cats=1-5 out=roads_net_all
    v.db.select roads_net_all

Result in matrix form:

    from\to	1		3		4		5
    1	0		18820.386	17206.651	17373.274
    3	18820.386	0		1739.079	9040.575
    4	17206.651	1739.079	0		7426.84
    5	17373.274	9040.575	7426.84		0

## SEE ALSO

v.net.path, v.net.distance

## AUTHORS

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

Last changed: $Date$