Question: How do I access edge attributes?

[Remmargyp]

Hi! I'm using sfnetworks for a routing algorithm where the inputs are a street-network (shp that is translated to a graph) and a sequence of coordinate-pairs. The algorithm calculates the route between each coordinate pair and creates a dataframe (output) that saves the ids of all edges used by the shortest path. However, I would like to store in the output-dataframe custom ids (called 'LINK_ID', which can be found in the edges of the shapefile).

If I call the graph (with active edges) by typing its name in the console, I can see that the LINK_ID is stored for each edge, but I don't know how to access it. I know that this is a simple issue but I'm stuck.

Thanks for all input!

[loreabad6]

Hello @Remmargyp thank you for opening your issue. I hope you don't mind that I turned it into a discussion with the Q&A category. It is a bit difficult to help you without a reproducible example (see info on how to create a reprex here) and maybe a subset of your data. Can you prepare something like that to illustrate your problem?

[loreabad6]

As a first thought of what you are looking for:

graph %>%
    activate("edges") %>%
    as_tibble() %>%
    select(LINK_ID)

[Remmargyp]

Hey @loreabad6, thank you for your quick reply. I apologize for the lack of a reproducible example, but your reply worked for me! It gives me a data frame with two columns: LINK_ID and geometry.

To be sure that I'm doing the next step correctly I have the following question:

path <- st_network_paths(graph, from = a, to = b)
example_vector <- path$edge_paths

The values that are stored in the example_vector above (a and b being two coordinate pairs); do they correspond to the index of each edge in the graph or to the first attribute stored in the column? >> EDIT: Figured it out: yes they do.

Thanks a lot!

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A minor detail in response to your anwser: I think it's %>%, not %<%.