Hot answers tagged routing
source and target attribute contain node ID's. Each node ID should be unique, but it can appear multiple times in source and target column, because a node can be the connecting point for more than one road link. Depending of the direction (defined by the geometry) of the road link the node ID is source or target.
Actually you can use two tools, both are easy to install on your own server. OSRM writen in C++ and Lua GraphHopper if you prefer Java
Just to close this loose end, since I asked the question a new package was released called osmar which contains a vignette of how to implement shortest path algorithms in R using Open Street Map data: http://osmar.r-forge.r-project.org/ . It uses the function get.shortest.paths from the igraph package. Excellent article on this can be found here: ...
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