[Qgis-user] polygon centroids

[Siki Zoltan]

AFAIK xmin, ymin is not available in QGIS 2.2, you must upgrade to 2.4.

Zoltan

On Thu, 28 Aug 2014, Alexandre Neto wrote:

> Ups, my bad...
>
> You can get your features centroid using the function centroid(). It will
> return a point geometry, then you can get the x and y by using either x_min
> or x_max and y_min or y_max. Like this:
>
>  xmin( centroid( $geometry )) || ' , ' || ymin( centroid( $geometry ))
>
> Alexandre Neto
>
>
> On Thu, Aug 28, 2014 at 10:29 AM, Leo Kris Palao <lk.palao at gmail.com> wrote:
>
>> Hi Alexander,
>>
>> Thanks for your reply. In my understanding, this only applies if I have
>> point coordinates, right? If I have polygons I think I need another syntax?
>>
>> I can create centroids in Vector > Geometry > Polygon Centroids tool then
>> apply $x and $y to extract lat lon coordinates, but in some cases I want to
>> skip this process if I am dealing with more than 300 thousand features in
>> my polygon layer.
>>
>> Thanks,
>> -Leo
>>
>>
>> On Thu, Aug 28, 2014 at 3:01 PM, Alexandre Neto <senhor.neto at gmail.com>
>> wrote:
>>
>>> Hello Leo,
>>>
>>> That's quite straightforward actually. In the field calculator (or in any
>>> other instance of expression builder) there are 2 geometry functions to
>>> achieve what you need,  $x and $y.
>>>
>>> You can either put them in separate fields or create a string to populate
>>> a single one. Something like this,
>>>
>>> $x || ' , ' || $y
>>>
>>> Would produce something like this:
>>>
>>> '1234.56 , 9876.43'
>>>
>>> Notice that the double pipe character || works as a string concatenator.
>>> And that the result is a string therefore not useful for any arithmetic
>>> operations after.
>>>
>>> Hope this helped.
>>>
>>> Best regards,
>>>
>>> Alexandre Neto
>>> Em 27/08/2014 22:37, "Leo Kris Palao" <lk.palao at gmail.com> escreveu:
>>>
>>>> Hi QGIS users,
>>>>
>>>> I don't know if this question has been asked before.
>>>>
>>>> Can you help me create a syntax in field calculator to add in the
>>>> attribute table the centroids coordinates for each or selected polygon
>>>> features?
>>>>
>>>> I am using Qgis 2.2 "Valmiera" version in Windows.
>>>>
>>>> Thanks in advance for help,
>>>> -Leo
>>>>
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>>>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>>>>
>>>
>>
>