[GRASS-user] select areas

GRASS GRASS user
1

Hi everybody,

I want to select areas that don’t overlap with points, using “v.select -r […] operator=overlap”, I get unclosed boundaries and centroids at the places where an area is neighbour of a selected area. I do not understand how to obtain also the common border so to obtain closed boundaries with centroids (areas). I’m using GRASS 6.4, and imported the map of areas from a shapefile…

Thanks, and sorry for the simple question.

Daniel

2

Hello Daniel,

What about using operator=contains and -r flag? Does that work?

You may also want to update to GRASS 7. Check the manual for v.select [0] there, it has been improved a lot with examples for most (if not all) operators

Best,
Vero

[0] https://grass.osgeo.org/grass70/manuals/v.select.html

···

2016-03-19 5:39 GMT-03:00 Daniel Torres <nobeeakon@gmail.com>:

Hi everybody,

I want to select areas that don’t overlap with points, using “v.select -r […] operator=overlap”, I get unclosed boundaries and centroids at the places where an area is neighbour of a selected area. I do not understand how to obtain also the common border so to obtain closed boundaries with centroids (areas). I’m using GRASS 6.4, and imported the map of areas from a shapefile…

Thanks, and sorry for the simple question.

Daniel

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3

Thanks for the answer Veronica, sadly it didn’t worked. As far as I understand, using v.select with the flag -r , selects the common boundary first, so it is the excluded when in the reverse selection is done, don’t understand how exactly to solve that using only v.select. Instead I v.select(ed) -r , then v.extract centroids, and finally v.select areas that overlap with centroids.

Meanwhile waiting for the beautiful GRASS 7 for Debian.

Thanks again, and nice day.

Daniel

···

On Sat, Mar 19, 2016 at 3:07 PM, Veronica Andreo <veroandreo@gmail.com> wrote:

Hello Daniel,

What about using operator=contains and -r flag? Does that work?

You may also want to update to GRASS 7. Check the manual for v.select [0] there, it has been improved a lot with examples for most (if not all) operators

Best,
Vero

[0] https://grass.osgeo.org/grass70/manuals/v.select.html

2016-03-19 5:39 GMT-03:00 Daniel Torres <nobeeakon@gmail.com>:

Hi everybody,

I want to select areas that don’t overlap with points, using “v.select -r […] operator=overlap”, I get unclosed boundaries and centroids at the places where an area is neighbour of a selected area. I do not understand how to obtain also the common border so to obtain closed boundaries with centroids (areas). I’m using GRASS 6.4, and imported the map of areas from a shapefile…

Thanks, and sorry for the simple question.

Daniel

grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

4

On 20/03/16 06:10, Daniel Torres wrote:

Thanks for the answer Veronica, sadly it didn't worked. As far as I
understand, using v.select with the flag -r , selects the common
boundary first, so it is the excluded when in the reverse selection is
done, don't understand how exactly to solve that using only v.select.
Instead I v.select(ed) -r , then v.extract centroids, and finally
v.select areas that overlap with centroids.

I don't really understand why there are "common boundaries" between points and areas ? Could you provide a reproducible example, using the NC demo data, so that we can understand what exactly is the issue ?

Moritz

5

On Sat, Mar 19, 2016 at 9:39 AM, Daniel Torres <nobeeakon@gmail.com> wrote:

Hi everybody,

I want to select areas that don't overlap with points, using "v.select -r
[...] operator=overlap", I get unclosed boundaries and centroids at the
places where an area is neighbour of a selected area. I do not understand
how to obtain also the common border so to obtain closed boundaries with
centroids (areas). I'm using GRASS 6.4, and imported the map of areas from a
shapefile...

I could reproduce this: all boundaries of areas that overlap with
points are not written to the output when using v.select -r. This
caused unclosed boundaries of neighboring unselected areas. Fixed in
trunk r68110 and relbr70 r68111. You will need to wait for GRASS 7.0.4
or compile GRASS 7 yourself (easy on Debian).

Thanks, and sorry for the simple question.

That was not at all a simple question, thanks for reporting the problem!

Markus M