[Qgis-user] Line dissolve

[Charles Dixon-Paver]

Hi Nicolas, I would urge you to try again as I was sure this would work and
when I tested it I had no issues (using freshly digitized data). Maybe you
need to run a snapping operation first?

One issue is that intersecting lines may break your ability to retrieve
attributes with aggregates. For example, I ran the following on my Single
parts geometries in the field calculator:

aggregate(layer:='lines',aggregate:='concatenate_unique',concatenator:=',',expression:=
"idtext",filter:=within( $geometry, geometry(@parent)))

This initially had no issue getting all the matching line info, but as
soon as I added an intersecting line, the multipart to singlepart operation
splits those lines at the intersections, which results in a mismatch in the
retrieved attributes. Of course you could use an intersects() filter
instead, but then you'll be getting the intersecting lines attributes
concatenated as well...

Regards

On Sun, 29 Aug 2021 at 17:18, Nicolas Cadieux <njacadieux.gitlab at gmail.com>
wrote:

> Hi,
>
> Yes, Harrissou,
> 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. I did see a merge function but did not find the line_merge
> plugin in  the repository. I figured it was QGIS2 and had been dropped.  Do
> you have any info of this?
>
> Nicolas Cadieux
> https://gitlab.com/njacadieux
>
> Le 29 août 2021 à 00:53, DelazJ <delazj at gmail.com> a écrit :
>
> Hi Nicolas,
>
> What about using "Dissolve" and then "multiparts to singleparts"...
> There's also the line_merge function, if you want to go the expression
> route.
>
> Regards,
> Harrissou
>
> Le 29 août 2021 05:26:24 GMT+02:00, Nicolas Cadieux <
> njacadieux.gitlab at gmail.com> a écrit :
>>
>> Hi,
>>
>> Just to clarify, I have no attribute to dissolve the lines on… so If you
>> have as easy way to create an attribute list of all connected lines groups,
>> I would also appreciate it.  This is easy in strait python but I am making
>> a model and trying to rely on existing algorithms.
>> Thanks!
>>
>> Nicolas Cadieux
>> https://gitlab.com/njacadieux
>>
>> Le 28 août 2021 à 20:21, Nicolas Cadieux <njacadieux.gitlab at gmail.com> a
>> écrit :
>>
>> 
>> Hi,
>>
>> Is there an easy way, in processing, to dissolve lines that are touching?
>> Alternative, can I create a multilinestring with all the lines that are
>> touching?  Seems this should be a basic tool to have in QGIS…
>>
>> Nicolas Cadieux
>> https://gitlab.com/njacadieux
>>
>> --
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> brièveté.
>
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