[QGIS-Developer] Processing 3.0: Possible change to the Convex Hull algorithm

Paolo Cavallini cavallini at faunalia.it
Thu Jun 29 00:04:00 PDT 2017

Il 29/06/2017 08:33, Nyall Dawson ha scritto:
> On 28 June 2017 at 18:23, G. Allegri <giohappy at gmail.com> wrote:
>> The best of two (but there would be a bit of overhead for the algorithm):
>> set them to null as soon as two different values are found, keep the first
>> encountered value otherwise (all the features with same value).
> Ok - I've actually had a bit of a change of mind here, and am backing
> down from my "single function modular algorithm" stance.
> I'll keep the grouping option but will refine it's behavior. I propose:
> 1. Allowing multiple field selection for grouping
> 2. Keeping attributes of first feature when grouping
> 3. Dropping the "mode" selection combo - if fields are selected, the
> grouping occurs. If not, no grouping - per feature hull is made.
> I'll leave the possible inclusion of a "whole layer" hull as a
> separate future enhancement.

IMHO this last is a far more common requirement for users compared to
one hull per feature. Or, in fact, your approach makes sense to me for
polygons and lines, not for points. Of course having two different
behaviours of the same command for two different layer types is even
more puzzling.
All the best.

Paolo Cavallini - www.faunalia.eu
QGIS & PostGIS courses: http://www.faunalia.eu/training.html

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