I am trying to connect points in a vector layer. Each point should be connected to its nearest neighbour that is not inside the same polygon. I am using the ProcessX "nearest point to path" function, but I didn't find a proper expression. The points have an attribute with the name of the Polygon, which I wanted to use for that.
Looking at the figure: The whole idea is to separate the yellow areas (roads) at each crossing in case someone has a better idea.
You can create a virtual layer that will join the two layers, create the line and apply the desired filtering.
go to the menu Layer > Add Layer > Add/Edit Virtual Layer... and enter the query
SELECT pt1.id, pt2.id,
ROUND(MIN(ST_Distance(pt1.geometry, pt2.geometry)),2) AS distance,
MAKELINE(pt1.geometry, pt2.geometry) AS geometry
FROM point_layer AS pt1, point_layer AS pt2
WHERE pt1.polygon_name <> pt2.polygon_name
GROUP BY pt1.id
ORDER BY distance DESC
The group by will ensure we get a single result for each row in point_layer. Because we order by distance, the group by will retain the 1st entry, i.e. the nearest one.
