Re: [Qgis-user] points to polygons conversion

2022-03-16 Thread Nicolas Cadieux via Qgis-user 

Hi,

Unfortunately,  the $geometry field with the original polygons no longer 
exists.  Layers only have one geometry field at a time unless you 
specifically create something like a wkt of wkb field.


If it's was a regular grid, then yes, you could recreate it using 
vector/research tools/create grid.  As suggested, a Voronoi Polygons 
could work or maybe a tin mesh...  If you are on Windows 10 and have 
activated the file versioning, maybe you have an old copy of the file.


Nicolas

On 2022-03-16 12:08 p.m., chris hermansen via Qgis-user wrote:

Francesca and list,

On Wed, Mar 16, 2022, 03:06 Francesca Parente via Qgis-user 
 wrote:


Hello group,

I'd have a question I hope it doesn't sound too nonsense to you:
I'm working on a points shapefile, which I know has been created
by centroids of polygons- but I don't have access to polygonal areas.
I would need to select just those in some locations and recover
their original area within polygonal borders.

Is there a chance I can get it done by having this shapefile of
centroids only?!


Polygon centroids aren't necessarily inside polygons, so selecting 
centroids that fall within other areas doesn't mean the original 
polygons would also lie within those areas.


Also if you are trying to determine the proportion of the original 
polygons within the other areas (the intersections of the two sets) 
you must have the original polygons.


I doubt that answers achieved with only the centroids would provide 
any meaningful results.


Chris

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--
Nicolas Cadieux
https://gitlab.com/njacadieux
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Re: [Qgis-user] points to polygons conversion

2022-03-16 Thread chris hermansen via Qgis-user 
Francesca and list,

On Wed, Mar 16, 2022, 03:06 Francesca Parente via Qgis-user <
qgis-user@lists.osgeo.org> wrote:

> Hello group,
>
> I'd have a question I hope it doesn't sound too nonsense to you: I'm
> working on a points shapefile, which I know has been created by centroids
> of polygons- but I don't have access to polygonal areas.
> I would need to select just those in some locations and recover their
> original area within polygonal borders.
>
> Is there a chance I can get it done by having this shapefile of centroids
> only?!
>

Polygon centroids aren't necessarily inside polygons, so selecting
centroids that fall within other areas doesn't mean the original polygons
would also lie within those areas.

Also if you are trying to determine the proportion of the original polygons
within the other areas (the intersections of the two sets) you must have
the original polygons.

I doubt that answers achieved with only the centroids would provide any
meaningful results.

Chris
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Re: [Qgis-user] points to polygons conversion

2022-03-16 Thread Bernd Vogelgesang via Qgis-user 

Well, yes, thats sounds like nonsense ;)

The only thing I could think of is trying to make voronoi polygons
(toolbox) on those centroids, but for sure this will not bring up any
usefull findings.




Am 16.03.22 um 11:04 schrieb Francesca Parente via Qgis-user:

Hello group,

I'd have a question I hope it doesn't sound too nonsense to you: I'm
working on a points shapefile, which I know has been created by
centroids of polygons- but I don't have access to polygonal areas.
I would need to select just those in some locations and recover their
original area within polygonal borders.

Is there a chance I can get it done by having this shapefile of
centroids only?!

Thanks a lot for your time and good day to all,
Francesca
--

Francesca Parente

_ SESS Euro PhD
 in
SocioEconomic and Statistical Studies
_ Luiss SEP  School of European Political Economy

email: francescaparente@gmail.com
paren...@luiss.it


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[Qgis-user] points to polygons conversion

2022-03-16 Thread Francesca Parente via Qgis-user 
Hello group,

I'd have a question I hope it doesn't sound too nonsense to you: I'm
working on a points shapefile, which I know has been created by centroids
of polygons- but I don't have access to polygonal areas.
I would need to select just those in some locations and recover their
original area within polygonal borders.

Is there a chance I can get it done by having this shapefile of centroids
only?!

Thanks a lot for your time and good day to all,
Francesca
-- 

Francesca Parente

_ SESS Euro PhD
 in
SocioEconomic and Statistical Studies
_ Luiss SEP  School of European Political Economy

email: francescaparente@gmail.com
   paren...@luiss.it
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