Select points at the end of a line

Question

I have two layers in QGIS:

"line" layer which consists of lines and multi-lines
"Point" with points with attribute 'Code'

How to write a efficient script in PyQGIS to find out all the lines at whose

start point, there is a point with Code value "1" and
end point, there is a point with Code value "1"

Dear Rajesh Patnaik, I have seen your comment to @MBain answer, unfortunately it is not typical on GIS SE to request directly from a user some Python code without demonstrating any efforts of coding. It seems to me that your Question will be probably closed because of the missing attempts. So, I am highly suggesting to provide some code trials, otherwise MBain's answer looks valid to me. — Taras, Jul 27 '20 at 09:58
Maybe these threads Creating point at line end using QGIS or Can vector layer get start point and end point of line using PyQGIS? can help you to unravel your issue in a Python way. — Taras, Jul 27 '20 at 10:01

score 1 · Answer 1 · edited Jul 27 '20 at 09:54

1

You could add a Virtual Layer Layer|Add Layer|Add/Edit Virtual Layer... with the Query:

SELECT L.*
FROM "LineLayer" AS L, "PointLayer" AS P1, "PointLayer" AS P2
WHERE ST_Intersects(ST_PointN(L.geometry, -1), P1.geometry)
AND ST_Intersects(ST_PointN(L.geometry, 1), P2.geometry)
AND P1."Code" = 1
AND P2."Code" = 1

You would need to substitute "LineLayer" and "PointLayer" with the correct layer names.

This will select all the lines where the start point ST_PointN(L.geometry, 1) and end point ST_PointN(L.geometry, -1) each intersect points in the "PointLayer" where the "Code=1".

edited Jul 27 '20 at 09:54

Taras

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answered Jul 27 '20 at 08:33

M Bain

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Thanks. Can you please write it in python to run it in python console? – Rajesh Patnaik Jul 27 '20 at 09:34
I'm afraid not, SQL is more my strong point than Python. Good luck – M Bain Jul 27 '20 at 09:42
1

To be more precise with points I may be using ST_Equals() instead – Taras Jul 27 '20 at 09:55
@Taras, Thanks, didn't think of ST_Equals() – M Bain Jul 27 '20 at 10:26
1

BTW, in VL you can also use start_point() as well as end_point() – Taras Jul 27 '20 at 11:01

Select points at the end of a line

1 Answers1