## 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 alayer. 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 abcolumn 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: $Date$