Hi, The Expressions Plus plugin is there for sharing expressions that are of broader interest but for whatever reason did not make it (yet) to core [1]
Would be great to push there whatever is interesting so we don't have to install a bazillion different plugins. Matthias [1] https://plugins.qgis.org/plugins/qgsexpressionsplus/ On 19/10/16 21:42, DelazJ wrote: > Hi all, > Thank you all for your answers. This is really a great community! I > already knew that but let me say it loudly. It also shows all the > capabilities of QGIS to solve a problem. > > Nicolas, as Andreas said, I'm looking for something dynamic, live. > > The virtual layer can indeed be an option despite the creation of an > intermediate but somehow live layer. Would be nice to have Andreas > questions documented in the user manual so that users are fully aware > of any potential limitations of the feature or its great power. > > Another powerful feature I often neglect is the function editor. Maybe > because there are so many functions in the list that I end up thinking > that their combination would be enough. I think it's the way I will go > as no intermediate layer is involved and despite your remarks (which > are not far from Andreas questions about virtual layers). Thank you > Germán for reminding me. > That makes me wonder: we have in QGIS, ways to share processing > scripts and models, to share symbols, styles... What about something > to share custom expression functions? Plugins somehow already do that > but I think there are many people that have an operational code (that > fills some small and common needs like mine) but don't have > time/skills to create the Gui around. Does it sound > reasonable/feasible? Maybe should I open a discussion in dev list (or > a ticket)? > > Back to the approach I was following to solve the issue (combining > default functions in expression) may I understand that it was endless? > No way to group by when using aggregate function...? > > Greetings, > Harrissou > > Envoyé depuis mon HTC > > ----- Reply message ----- > De : "Germán Carrillo" <carrillo.ger...@gmail.com > <mailto:carrillo.ger...@gmail.com>> > Pour : "Neumann, Andreas" <a.neum...@carto.net > <mailto:a.neum...@carto.net>>, "Harrissou 'DelazJ'" <del...@gmail.com > <mailto:del...@gmail.com>> > Cc : "Nathan Woodrow" <madman...@gmail.com > <mailto:madman...@gmail.com>>, "qgis-user" <qgis-user@lists.osgeo.org > <mailto:qgis-user@lists.osgeo.org>>, "Nicolas Cadieux" > <nicolas.cadi...@archeotec.ca <mailto:nicolas.cadi...@archeotec.ca>> > Objet : [Qgis-user] Using aggregates functions to count intersected > features from another layer > Date : mer., oct. 19, 2016 18:04 > > Hi All, > > > Harrissou, have a look at [1] for a very similar question and one > possible solution using the Function Editor (of course, instead of sum > you would use count). > > Do you other devs find that approach useful? Any hint for keeping the > index up-to-date? > > Is there any interest in having this kind of functions available for > QGIS expressions? I could help with that. > > > Regards, > > Germán > -- > [1] http://gis.stackexchange.com/a/212762/4972 > <http://gis.stackexchange.com/a/212762/4972> > > > 2016-10-19 7:42 GMT-05:00 Neumann, Andreas <a.neum...@carto.net > <mailto:a.neum...@carto.net>>: > > Good idea to use a virtual layer for that! It is probably also > more efficient than a QGIS expression. > > Just to understand the virtual layers correctly: > > when is the query behind the virtual layer executed? > > - at every redraw? > > - once at creation? > > - at project reload? > > Aren't the virtual layers automatically updated, at least when the > project reloads? > > Are the results cached or not? > > Would also make sense to add a "update" option for a virtual > layer, if that doesn't exist yet. > > Greetings, > > Andreas > > > > On 2016-10-19 14:32, Nathan Woodrow wrote: > >> Maybe using a virtual layer query via DB Manager will work. You >> have full SQL join support. Speed isn't always the best but gives >> you the full power of SQL which is the correct way to do this IMO. >> >> E.g SELECT LayerA.id, COUNT(*) FROM layerA >> JOIN layerB ON ST_WithIn(layerA.geometry, layerB.geometry) >> GROUP BY layerA.type >> >> Although you can't do an update but you can make a new layer with >> the new counts. >> >> - Nathan >> >> On Wed, Oct 19, 2016 at 10:22 PM, Neumann, Andreas >> <a.neum...@carto.net <mailto:a.neum...@carto.net>> wrote: >> >> Well yes - but that is not a "live" point in polygon. It >> create separate layers which need to be kept up-to-date. >> >> Harrissou was after a "live" point in polygon, which is >> automatically kept up-to-date through a QGIS expression. >> >> Maybe Nyall knows how to write the correct aggregate >> expression for that? >> >> Greetings, >> >> Andreas >> >> On 2016-10-19 14:11, Nicolas Cadieux wrote: >> >> >> Try this. >> >> http://www.qgistutorials.com/fr/docs/points_in_polygon.html >> <http://www.qgistutorials.com/fr/docs/points_in_polygon.html> >> >> Nicolas >> >> Le 19 oct. 2016 à 06:37, DelazJ [via OSGeo.org >> <http://OSGeo.org>] <[hidden email]> a écrit : >> >> Hi, >> >> I have a polygon layer and a point one. >> I'd like to calculate for each polygon feature, the >> number of points that it covers. I thought the >> aggregates functions could help me find an easier and >> straight expression to perform this (without creating >> intermediate layers) but I fail to find any correct >> syntax. >> >> I tried aggregate ('mypoint', 'count', "id", >> intersects ($geometry, geometry($currentfeature))) >> >> And many variants of the fourth option but It always >> return the total of points or an error. Actually this >> option is a filter and I wonder if i'm not missing a >> "group by" option in the aggregate function (which >> seems to be the appropriate one in my case). Is it >> possible? >> The work around I found is to populate an ad'hoc >> field in the point layer with overlapping polygon id, >> thanks to the SpatialJoin plugin, then I create a >> one-to-many relation in the project between the two >> layers in other to use relation_aggregate function. >> But I expected something more direct. >> >> Any hint, please? >> >> Thanks, >> Harrissou >> >> _______________________________________________ >> Qgis-user mailing list >> [hidden email] >> List info: >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> <http://lists.osgeo.org/mailman/listinfo/qgis-user> >> Unsubscribe: >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> <http://lists.osgeo.org/mailman/listinfo/qgis-user> >> >> >> ------------------------------------------------------------------------ >> If you reply to this email, your message will be >> added to the discussion below: >> >> http://osgeo-org.1560.x6.nabble.com/Using-aggregates-functions-to-count-intersected-features-from-another-layer-tp5291420.html >> >> <http://osgeo-org.1560.x6.nabble.com/Using-aggregates-functions-to-count-intersected-features-from-another-layer-tp5291420.html> >> To start a new topic under Quantum GIS - User, email >> [hidden email] >> To unsubscribe from Quantum GIS - User, click here. >> NAML >> >> <http://osgeo-org.1560.x6.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> >> >> >> >> ------------------------------------------------------------------------ >> View this message in context: Re: Using aggregates >> functions to count intersected features from another >> layer >> >> <http://osgeo-org.1560.x6.nabble.com/Using-aggregates-functions-to-count-intersected-features-from-another-layer-tp5291420p5291443.html> >> Sent from the Quantum GIS - User mailing list archive >> >> <http://osgeo-org.1560.x6.nabble.com/Quantum-GIS-User-f4125267.html> >> at Nabble.com. >> >> _______________________________________________ >> Qgis-user mailing list >> Qgis-user@lists.osgeo.org <mailto:Qgis-user@lists.osgeo.org> >> List info: >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> <http://lists.osgeo.org/mailman/listinfo/qgis-user> >> Unsubscribe: >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> <http://lists.osgeo.org/mailman/listinfo/qgis-user> >> >> >> >> >> >> _______________________________________________ >> Qgis-user mailing list >> Qgis-user@lists.osgeo.org <mailto:Qgis-user@lists.osgeo.org> >> List info: http://lists.osgeo.org/mailman/listinfo/qgis-user >> <http://lists.osgeo.org/mailman/listinfo/qgis-user> >> Unsubscribe: >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> <http://lists.osgeo.org/mailman/listinfo/qgis-user> >> > > > > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org <mailto:Qgis-user@lists.osgeo.org> > List info: http://lists.osgeo.org/mailman/listinfo/qgis-user > <http://lists.osgeo.org/mailman/listinfo/qgis-user> > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user > <http://lists.osgeo.org/mailman/listinfo/qgis-user> > > > > > -- > ----------- > |\__ > (:>__)( > |/ > Soluciones Geoinformáticas Libres > http://geotux.tuxfamily.org/ > http://twitter.com/GeoTux2 > http://about.me/germancarrillo > > <http://gis.stackexchange.com/users/4972/germ%c3%a1n-carrillo> > > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: http://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-user
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