# Return the nodes that can be reached in a detour time set around the shortest path ```r get_detour(Graph, from, to, extra = NULL, keep = NULL, long = FALSE) ``` ## Arguments - `Graph`: An object generated by makegraph or cpp_simplify function. - `from`: A vector of one or more vertices from which shortest path are calculated (origin). - `to`: A vector of one or more vertices (destination). - `extra`: numeric. Additional cost - `keep`: numeric or character. Vertices of interest that will be returned. - `long`: logical. If `TRUE`, a long `data.frame` is returned instead of a list. ## Returns `list` or a `data.frame` of nodes that can be reached ## Details Each returned nodes **n** meet the following condition : SP(o,n) + SP(n,d) \< SP(o,d) + t with **SP** shortest distance/time, **o** the origin node, **d** the destination node and **t** the extra cost. Modified bidirectional Dijkstra algorithm is ran for each path. This algorithm is multithreaded. Please use `RcppParallel::setThreadOptions()` to set the number of threads. ## Note `from` and `to` must be the same length. ## Examples ```r #Choose number of cores used by cppRouting RcppParallel::setThreadOptions(numThreads = 1) if(requireNamespace("igraph",quietly = TRUE)){ #Generate fully connected graph gf<- igraph::make_full_graph(400) igraph::V(gf)$names<-1:400 #Convert to data frame and add random weights df<-igraph::as_long_data_frame(gf) df$dist<-sample(1:100,nrow(df),replace = TRUE) #Construct cppRouting graph graph<-makegraph(df[,c(1,2,5)],directed = FALSE) #Pick up random origin and destination node origin<-sample(1:400,1) destination<-sample(1:400,1) #Compute distance from origin to all nodes or_to_all<-get_distance_matrix(graph,from=origin,to=1:400) #Compute distance from all nodes to destination all_to_dest<-get_distance_matrix(graph,from=1:400,to=destination,) #Get all shortest paths from origin to destination, passing by each node of the graph total_paths<-rowSums(cbind(t(or_to_all),all_to_dest)) #Compute shortest path between origin and destination distance<-get_distance_pair(graph,from=origin,to=destination) #Compute detour with an additional cost of 3 det<-get_detour(graph,from=origin,to=destination,extra=3) #Check result validity length(unlist(det)) length(total_paths[total_paths < distance + 3]) } ```

get_detour function