Calculating Driving Distances using sfnetworks about sfnetworks

[loreabad6]

Hi @swaheera,

After reviewing your code I see a couple of issues.

1. The way you define your start and end points is not entirely correct. When you set the CRS, you are basically telling sf to assign a EPSG:3347 to coordinates that actually are in EPSG:4326 as given above. To correct this you should do something like:

q1 <- st_transform(st_sfc(q1, crs = st_crs(4326)) , st_crs(a))
q2 <- st_transform(st_sfc(q2, crs = st_crs(4326)) , st_crs(a))

2. When you create the network as_sfnetwork() defaults to directed networks. This usually is a tricky setting knowing that many road networks are not correctly digitized. The algorithm doesnot find a path between your points because of the direction of the edges. To avoid this you can use:

net <- as_sfnetwork(a, directed = FALSE)

3. In your original code you were getting a result already stored on the paths object. This is where all the nodes and edges of you resulting path are located as list objects. If you are only looking for the distance however, I would recommend you to call st_network_cost(net, q1, q2). This will directly give you the shortest network distance in meters between your two points.

If hope you don't mind that I convert this issue to a discussion. If you have any question we can discuss there 😄