[Qgis-user] Group Statistics Tool

[krishna Ayyala]

When I enter the Polygon in the column field and calculate, I am getting
like this. When I select row 2 and Click Features --- Show Selected on map,
all the four polygons are getting highlighted.

[image: image.png]

On Sun, Jul 18, 2021 at 12:40 PM Nicolas Cadieux <
njacadieux.gitlab at gmail.com> wrote:

> Hi,
>
> This is like a cross tab or a pivot table in Excel. You need to place the
> polygon layer in the column field.
>
> https://anitagraser.com/2013/02/02/group-stats-tutorial/
>
> Nicolas Cadieux
> https://gitlab.com/njacadieux
>
> Le 18 juill. 2021 à 12:47, krishna Ayyala <ayyalakrishna at gmail.com> a
> écrit :
>
> 
> Nicolas,
> Thanks for your reply.They are not multi polygons. They are two
> separate polygons. That means A with area 60 is one polygon and A with area
> 30 is second polygon. If I select one polygon on the map, only one polygon
> gets highlighted. But, in group stats ,I have selected the first row which
> is A 60. I clicked "Features" and then "Show selected on map" both the
> polygons on the map are getting highlighted. As I mentioned before, only
> one polygon should get highlighted. If I create a unique id, that will not
> serve the purpose. I am trying to derive the polygon with maximum area
> from the list of polygons that are labeled as A.
>
> Regards.
>
> On Sun, Jul 18, 2021 at 9:58 AM Nicolas Cadieux <
> njacadieux.gitlab at gmail.com> wrote:
>
>> Hi,
>>
>> I do you have multipolygons in your input files?  If not, perhaps the
>> multipolygon is being created because both polygon have the same ID, A.
>> Try creating a unique id field to see what is going on.  A multipolygon or
>> multipart object will contain multiple polygons but only one data line in
>> the data table. You can split multipolygon with a «multiple to single »tool
>> found in the vector menu.
>>
>> Nicolas Cadieux
>> https://gitlab.com/njacadieux
>>
>> Le 17 juill. 2021 à 20:56, krishna Ayyala <ayyalakrishna at gmail.com> a
>> écrit :
>>
>> 
>> Hello,
>> I have a polygon shape file with an attribute table as shown below.
>>
>> <image.png>
>>
>>
>> I am using the Group stats tool to derive only those rows that have max
>> area for each polygon. After clicking calculate, I got the results below.
>> In the below window. I have selected the first row which A 60. I clicked
>> "Features" and then "Show selected on map" . Technically, it is supposed to
>> highlight only one polygon which is A with an area 60 on the map. But is
>> highlighting both the polygons i.e..A with an area 60 and also A with an
>> area 30. Is there a way to select only the polygon A with an area 60?
>>
>> <image.png>
>>
>>
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