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I have a network of roads and I would like to obtain a graph made by edges, each of them delimited by a origin node and a end node, such as the picture shows.

Edges with nodes

I would like to obtain a table made of rows like this

"edge_id, origin_node_id, end_node_id, origin_node_X, origin_node_Y, end_node_X, end_node_Y"

for example, for the a12 edge: "a12, 48.1234, 50.0000, 48.1335, 49.1111", where the origin node 1 coordinates are (48.1234,50.0000) and the end node 2 coordinates are (48.1335,49.1111). I used the field calculator with these expressions:

x_at(0),y_at(0),x_at(1),y_at(1)

to get "origin_node_X,origin_node_Y,end_node_X,end_node_Y".

Now I am searching for a way to obtain the id of nodes which obviously are in another layer.

So I think that I could need a field calculator expression or python code to relate nodes' layer with edges' layer. I think that "get_feature" could be useful but at the moment I did not find the right way to use it. Another option is to make a text output file with python.

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    The term you are looking for is "cross section" gis.stackexchange.com/questions/30018/… without details this might be a duplicate question – risail Dec 27 '16 at 18:50
  • @risail and others - the two questions don't seem related at all to the uninformed (me!), could someone explain why this is a duplicate? – Simbamangu Dec 28 '16 at 6:47
  • It's a possible duplicate if the OP was more specific it may not be...but how to create a cross section in qgis is well documented here. More details are needed – risail Dec 28 '16 at 6:56
  • I do not think that could be a duplicate of cross section. I am uninformed, but I read the cross section question and it does not help me – Giacomo Dec 28 '16 at 22:07
  • Welcome to gis.stackexchange! Please note that a good question on this site is expected to show some degree of research on your part, i.e. what you have tried and - if applicable - code so far. For more info, you can check our faq. – underdark Dec 29 '16 at 0:59
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I made a spatial join with [min,max] between the edges layer and the nodes layer so as to have the origin node as the minimum and the end node as the maximum

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