[QGIS-ZA-user] Polygon Centroids Extraction - New User

[Frank Sokolic]

Hi Herbert,

The attribute table of the Centroids file should have the cluster number 
as one of the attributes (let me know if it doesn't). You can then do 
the following:

1) Add the X/Y coordinates to the Centroids attribute table (from the 
menu bar select Vector > Geometry Tools > Add Geometry Attributes).
2) In the Layers panel, right-click on the name of the new layer 
produced in step 1 (it will be something like "Added geom info") and 
select "Export > Save features as". Set the format to "Comma separated 
value" and save the file.

That should do it.

Regards, Frank

On 2021/03/04 08:54, Herbert Chitate wrote:
> Hi Frank,
>
> You are an absolute life saver. Almost there. So I managed to generate 
> the centroids. Thoroughly impressed for a new user!!!
>
> I have attached a screen shot of the results.
>
> Final question though is how do I extract the lat and lon of the 
> centroids, into say a csv file with also a column with the cluster 
> number they belong to (cluster number is what i used to demacate the 
> different polygons in step 2 of your instructions)
>
> Many many many thanks
>
> Much appreciated
>
> Regards
>
> Herbert
>
> On Mon, Mar 1, 2021 at 2:25 PM Frank Sokolic via qgis-za-user 
> <qgis-za-user at lists.osgeo.org <mailto:qgis-za-user at lists.osgeo.org>> 
> wrote:
>
>     Hi Herbert,
>
>     I haven't tested it but you could try something like this:
>
>     1) Load the csv file into QGIS using the "Add Delimited Text
>     Layer" tool (Shift + Ctrl + T)
>     2) Use the "Minimum bounding geometry" tool to create a polygon
>     around each cluster (Processing Toolbox > Vector geometry >
>     Minimum bounding geometry)
>     3) Generate centroids for each polygon (Processing Toolbox >
>     Vector geometry > Centroids)
>
>     Hope this helps.
>
>     Regards, Frank.
>
>     On 2021/03/01 13:04, Herbert Chitate via qgis-za-user wrote:
>>     Good afternoon All,
>>
>>     I am new to QGIS and was wondering if someone might be able to
>>     assist me on an extraction I am trying to do.
>>
>>     I have lat and lon details for about 1,500 locations, which using
>>     python (kmeans), I have clustered the data into 20 clusters of
>>     which I have the details of the constituent members (+ gps
>>     locations) that make up the 20 clusters. Info now in a CSV file.
>>
>>     How can I use QGIS to establish the lat and lon of the centroids
>>     for each of the clusters?
>>
>>     Thank you for the assistance.
>>
>>     Regards
>>
>>     Herbert
>>
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