[Qgis-user] Draw Ellipse/Polygons for areas of maximum concentration

[krishna Ayyala]

Nyall,
Thanks for your reply. I have used the "dbscan clustering". In this, the
default values for "Minimum Cluster Size" is 5 and Max distance between
cluster points is 1 degrees. I ran with the same default values. I am
getting output with the layer name "Clusters". This has generated a new
field "Cluster_ID". All the points have same Cluster_ID i.e. 1. This has
also generated new field called "Cluster_Size". All the points have same
cluster size i.e. 1699. Can you please help me on how to get 4 different
cluster ID's.

Regards.

On Thu, Apr 29, 2021 at 4:29 PM Nyall Dawson <nyall.dawson at gmail.com> wrote:

>
>
> On Fri, 30 Apr 2021 at 08:25, krishna Ayyala <ayyalakrishna at gmail.com>
> wrote:
>
>> Chris,
>> Thanks for the reply. Yes, I did run k-means clustering for 4 clusters.
>> It is creating a new layer called "clusters". This layer has a field called
>> Cluster_id, ranging from 1 to 4. But, this method is considering all the
>> points within the circle. I am looking for the points outside the ellipses
>> to be omitted (should not be considered)
>>
>
> In this case "dbscan clustering" is more appropriate.
>
>
>> . Also K-means clustering is not generating any polygons/ellipses. We
>> have to identify a cluster based on the Cluster_ID. I am curious if there
>> is any tool within Qgis that can produce results similar to the circle with
>> ellipses?
>>
>
> What you could do is dissolve the points based on the cluster_id field,
> and then generate convex (or concave) hulls enclosing each set of points.
> You won't get ellipses, but you'll get polygons describing the boundaries.
> (And it would be relatively straightforward to wrap up these steps into a
> single graphical model so that you have one tool which gives the desired
> output!).
>
> Nyall
>
>
>
>
>>
>> Regards.
>>
>> On Thu, Apr 29, 2021 at 3:56 PM chris hermansen <clhermansen at gmail.com>
>> wrote:
>>
>>> Krishna and list,
>>>
>>> On Thu, Apr 29, 2021 at 2:51 PM krishna Ayyala <ayyalakrishna at gmail.com>
>>> wrote:
>>>
>>>> Hello,
>>>> I have a circle in which there are randomly distributed points as
>>>> below. Each point is a customer.
>>>>
>>>> [image: image.png]
>>>>
>>>>
>>>> Is there a tool within QGIS that can automatically generate four
>>>> polygons or four ellipses such as below. These polygons are the areas of
>>>> maximum concentration of the customers?
>>>>
>>>> [image: image.png]
>>>>
>>>> You could try k-means clustering
>>>
>>>
>>> https://docs.qgis.org/3.4/en/docs/user_manual/processing_algs/qgis/vectoranalysis.html#k-means-clustering
>>>
>>> --
>>> Chris Hermansen · clhermansen "at" gmail "dot" com
>>>
>>> C'est ma façon de parler.
>>>
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