On 15/02/14 14:35, Markus Neteler wrote:
On Sun, Feb 9, 2014 at 8:13 PM, David Montoya <[email protected]
<mailto:[email protected]>> wrote:
Hi, I have a question. I need to generate a table that says which
polygons bordering to each one, for example:
ID1 ID2
1 3
1 2
2 1
2 4
3 1
3 4
3 5
4 2
4 3
4 6
5 3
5 6
6 4
6 5
In this case the polygon 1 borders with the polygons 3 and 2, and so
on. How can I do that in Grass?
The module v.to.db offers a "sides" option, perhaps that's useful here.
For an (un)related example, see
http://grasswiki.osgeo.org/wiki/Vector_length_of_common_boundaries
Rather the length you could then just retrieve the IDs.
A simple two-liner gets you a csv-file with the neighborhood matrix.
Example with the NC-dataset:
v.category boundary_county op=add layer=2 out=counties
v.to.db -p counties op=sides layer=2 qlayer=1 type=boundary > neighbors.csv
This matrix contains the -1 for "no neighbor" and some repetition of
pairs. You can use some awk, sort and uniq magic to clean that up:
v.to.db -p counties op=sides layer=2 qlayer=1 type=boundary | awk -F '|'
'{if($2!=-1 && $3 !=-1) printf"%i;%i\n", $2,$3}' | sort -n | uniq >
neigbhors.csv
Moritz
_______________________________________________
grass-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-user
