Hi, > That does not work with lines unfortunately. I tried multiple times with different combinations. It works with polygons when common borders need to be dissolved.
Nicolas, can you elaborate a bit more on the issues you have with the "Dissolve + Multipart to singleparts" solution I provided few days ago. At which step is it failing? The dissolve does not merge joining features into a single one? I don't know the function internals but I'd expect it to work this way and if not, would sound like a bug to report IMHO... Regards, Harrissou Le mar. 31 août 2021 à 00:57, Nicolas Cadieux <[email protected]> a écrit : > Thanks Charles, > > This will be very useful. Nice to know I'am not the only one going crazy > with this!!! > > Nicolas > On 2021-08-30 4:42 p.m., Charles Dixon-Paver wrote: > > I thought this would be easily solved with an expression but sadly I > haven't been able to get reliable results at all. > > My first thought was > collect($geometry,filter:=intersects($geometry,geometry(@parent))) and > when that didn't work I tried various aggregates and union operations to no > avail. Something like this might be useful if you can get it into a usable > form (I managed to get various multigeometries in the form you are looking > for but wasn't able to do much with them and there seemed to be artifacts): > > > collect_geometries(array_foreach(aggregate(layer:='lines',aggregate:='array_agg',expression:=$geometry,filter:=intersects($geometry,geometry(@parent))),@element)) > > I was actually waiting for someone else to come up with a more elegant > solution, but it would probably also be possible to identify intersecting > features and get the minimum/ maximum feature id for intersecting features > with this: > > aggregate(layer:='lines', > aggregate:='min', > expression:="fid", > filter:=intersects($geometry,geometry(@parent))) > > You could use that in the field calculator to create a field for > "grouping" various intersecting features to dissolve on, however it's only > going to identify the minimum of the currently intersecting features so you > would need to iterate through the process multiple times. I can't think of > an effective way to implement a "while" conditional either. > > It's a pretty clanky way to do it, but if you are really struggling I > think it's possible. > > On Mon, 30 Aug 2021 at 22:10, Nicolas Cadieux <[email protected]> > wrote: > >> Hi, >> >> Seems like the plugin is available so I will try it out. The ability to >> create multi-linestring out of any touching lines (touch here means >> intersects at the first or last node) would be nice to have it if I can >> include it in a model. >> >> My goal is for this model to work for anyone with a basic install of QGIS >> LTR or 3.20 with minimal efforts so I am trying to eliminate the need to >> rely on external plugins or scripts. >> >> This is also my first attempt with models. It’s a learning curve but I am >> having fun… I think this probably should have been a plugin but my >> knowledge of GUI programming is basically 0. That will be for a next >> project… >> >> Nicolas Cadieux >> https://gitlab.com/njacadieux >> >> Le 30 août 2021 à 14:59, David Strip <[email protected]> a >> écrit : >> >> I looked at the source for this plug-in and as far as I can tell it >> only merges lines that meet at endpoints. It ignores multi-lines, and only >> creates linestrings, so there are no vertices of degree >2 (ie, no >> junctions/forks). Also, the plug-in doesn't look for intersections between >> vertices (since it only looks to merge endpoints.) >> The StackExchange post appears to want multi-linestrings, which gives >> forks and such. Is that what you need? >> >> On 8/30/2021 5:27 AM, Nicolas Cadieux wrote: >> >> Hi, >> This is the plugin I was referring to. I don’t see it in the current >> plugins (experimental turned on) so I figured it’s QGIS 2 only. >> >> https://github.com/ArMoraer/QGISMergeLines >> >> Nicolas Cadieux >> https://gitlab.com/njacadieux >> >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> > -- > Nicolas Cadieuxhttps://gitlab.com/njacadieux > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >
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