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GRASS has extensive and brilliant documentation, but I still have a bit of trouble using in the example for shortest path, it says: "

#Shortest path: ID as first number, then cat1 and cat2

echo "1 1 2" | myroads_net_time alayer=3 nlayer=2 out=mypath"

I've had trouble understanding what ID is; my table has 'cat' as it's primary key, but there is no ID column.

Any ideas?

P.S. I'm using Grass 6.4 on Mac.

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Please post which GRASS GIS version you use. – markusN Mar 29 '13 at 12:20
up vote 2 down vote accepted

Here the "ID" (as first number) defines the ID of the shortest path to be calculated. This is followed by "cat1" and "cat2" of the nodes to be connected.

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