I would like to show arrowheads in the endings of every drawn linestring.
Is it possible in QGIS?
I have been trying to use a marker line but repeats all de arroheads all over the line, it is not restricted to the ends:
QGIS – Showing Arrowheads in Line End Using QGIS
qgissymbology
Related Solutions
I think that it might be easiest to do with ST_ShortestLine with PostGIS http://postgis.net/docs/ST_ShortestLine.html or with a similar ShortestLine function in Spatialite https://www.gaia-gis.it/gaia-sins/xmlBlob/spatialite-sql-latest.html.
You said you have only points but those functions can be used for other geometries as well.
Here is an example with Spatialite.
SELECT
shortestline(a.geometry,b.geometry) AS geometry,
a.rowid AS start,
b.rowid AS end
FROM
source_table a,
source_table b
WHERE
a.rowid < b.rowid;
You can use aggregate() with an intersects() filter:
aggregate(
'ok_ak_riks',
'concatenate',
"kommunkod",
filter:=intersects($geometry,end_point(geometry(@parent))),
concatenator:=','
)
Previous / alternative answer:
array_to_string(
array_filter(
array_foreach( -- 2. iterate over ALL intersecting features
overlay_intersects('ok_ak_riks',$currentfeature), -- 1. get ALL intersecting features
if(
intersects(geometry(@element),end_point($geometry)), -- 3. check if the current one intersects with the lines endpoint
attribute(@element,'kommunkod'), -- 4a. if it does, return the attribute
'' -- 4b. otherwise return an empty string
)
),
@element <> '') -- 5. filter out the empty strings from the array
)
Explanation:
you can first get all intersecting features as array by using overlay_intersects('ok_ak_riks',$currentfeature), then iterate over this array by using array_foreach() and filter to the intersecting ones with your endpoint by testing if the current one intersects with your endpoint if(intersects(geometry(@element),end_point($geometry)). This will return the feature of ok_ak_riks intersecting with the lines end. At this point you will get an array like ['','your attribute','',''] where you never know at which position your value is. So you can use array_filter(array,@element <> '') to remove all empty values.
Best Answer
QGIS 2.16. version has the option to make the arrows, like this.
