[GRASS-user] v.voronoi error: Found 0 points/centroids, but atleast 2 are needed

[Markus Metz]

On Sat, Nov 25, 2017 at 2:43 PM, 洪朝貴 <ckhung at cyut.edu.tw> wrote:
>
> Thank you Markus! It works now.
>
> Printing the current region could help.
> Re-wording the manual page may also help.
> "Unlike most other vector functions, setting the
> computation region is mandatory in order to deal with
> infinite regions in the Voronoi diagrams."
> Or something prominent like that.

The first line of the manual

"v.voronoi - Creates a Voronoi diagram in current region from an input
vector map containing points or centroids."

could be rephrased to

"v.voronoi - Creates a Voronoi diagram constrained to the extents of the
current region from an input vector map containing points or centroids."


> I read somewhere that vector operations are not
> affected by the region setting, and had success with
> v.distance and v.delaunay without ever setting it.
> The v.voronoi manual says
> "The  bounds  of  the  output map are limited by the current region."
> but I somehow ignored it as something to worry about later
> if and when I get some output :-)

It is something to worry about particularly when you get no output ;-)

We could change the error message

"Found 0 points/centroids in <tkec at work>, but at least 2 are needed"

to something like

"Found 0 points/centroids in <tkec at work>, but at least 2 are needed. Please
verify that the current region extents are covering at least parts of the
input map."

Markus M
>
>
>
> --
> 『我的野蠻工讀生』用高昂的『下賊船的代價』
> 綁架了我的文件! (請分別搜尋)
> Chao-Kuei Hung 洪朝貴
>
> PGP Key ID: 4096R/5828A7A7
> Fingerprint: 67AF B5AB 5242 3E99 16D7  EAF8 A94D 2C92 5828 A7A7
>
>
> 2017-11-25 20:48 GMT+08:00 Markus Neteler <neteler at osgeo.org>:
> > On Nov 25, 2017 11:48 AM, "Markus Metz" <markus.metz.giswork at gmail.com>
> > wrote:
> >> On Sat, Nov 25, 2017 at 3:07 AM, 洪朝貴 <ckhung at cyut.edu.tw> wrote:
> > ...
> >> > Did I miss some steps before calling v.voronoi?
> >>
> >> v.voronoi uses the current region (the algorithm requires this),
therefore
> >> you need to set an appropriate computational region first, e.g. with
> >>
> >> g.region -pa vect=tkec res=1
> >>
> >> before using v.voronoi.
> >
> > Would it make sense to print the used region settings to help the user?
> >
> > Best,
> > markusN
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-user/attachments/20171125/f4a1b0b6/attachment-0001.html>