flownet 0.3.0 introduces one new function for critical link analysis and substantive performance improvements to consolidate_graph() and simplify_network().
critical_link_analysis(): New function that computes edge-level detour costs and vulnerability ratios for any graph. For each edge (u, v) it finds the shortest alternative path from u to v after removing that edge, without repeated graph deletion. The underlying C implementation runs a multi-label Dijkstra once per unique source node, tracking the two best distances that begin via different first edges. Parallel edges are handled as distinct alternatives; edges with no detour receive Inf. Supports directed and undirected graphs, and parallelises per-source Dijkstra runs across nthreads OpenMP threads.Singleton-edge removal now uses a linear-time peel (drop_singletons_linear()), avoiding repeated full-graph scans on large networks.
Degree-2 chain contraction is now performed at C level (C_contract_linear_nodes) by default. The C routine walks each chain once using dense array indexing with no hash table. Set options(flownet.use_c_contraction = FALSE) to force the R-only fallback.
consolidate_graph_core() remaps from / to to dense internal node indices (funique.default() + fmatch()) before contraction and maps aggregated endpoints back to original node IDs, so results and downstream joins are unchanged.
consolidate_graph_core() now handles topology-only graphs (no coordinate or attribute columns): when no nodes are kept for aggregation, it correctly returns a data frame of contracted groups.
When verbose = TRUE, phase timings are reported for singleton peel, orientation, contraction, and aggregation steps.
More testthat coverage for edge cases: recursion, keep.nodes, long chains, C vs. R contraction equivalence, and singleton-peel equivalence.
New nthreads parameter (default 1): parallelises the per-chunk shortest-path computations in method = "shortest-paths" using mirai daemons, matching the multithreading interface of run_assignment().
New cluster.algo.dbscan parameter (default FALSE): when TRUE, spatial clustering of remaining nodes uses dbscan::dbscan() instead of leaderCluster. DBSCAN is substantially faster for larger datasets. Requires the dbscan package.
New nodes.algo.rann parameter (default FALSE): when TRUE, node-to-kept-node assignment uses RANN's fast k-d tree nearest-neighbour search on 3-D Cartesian coordinates (converted from lon/lat via lonlat_to_xyz()). Requires the RANN package.
The simplified graph returned by method = "cluster" now carries a keep.edges attribute containing the integer indices of the edges retained from the original graph.
simplify_network(method = "shortest-paths"): the two result attributes have been renamed for consistency with the cluster method and consolidate_graph():
"edges" → "keep.edges" (integer vector of retained edge indices)"edge_counts" → "edge.counts" (traversal counts for each retained edge)
Update any code that reads attr(result, "edges") or attr(result, "edge_counts").consolidate_graph() attaches keep.edges and group.id together (aligned, same length) for recursive = "none" or "partial"; with the default recursive = "full" they are omitted (the mapping would span multiple passes), which is now stated in the documentation. create_undirected_graph() now also exposes group.id and group.sizes (previously only group.starts, and undocumented), and consolidate_graph() strips any stale grouping attributes carried in from upstream operations.Fixed issue in consolidate_graph() which used to modify columns (from and to in-place). Users in older versions are advised to input a data.table::copy() of the graph to retain it.
Fixes issue with multithreading for newer versions of mirai (or R). Thanks @kent37 (#69).
angle.max constraint in run_assignment() is now two-sided (angle measured from origin and destination node against the straight line between them), rather than just one-sided (from origin). Also, the implementation is slightly more efficient.Release blog post at: https://sebkrantz.github.io/Rblog/2026/02/09/introducing-flownet-efficient-transport-modeling-in-r/
Fixed bug in run_assignment with return.extra = "edges" where edge indices were incorrectly returned. Due to zero indexing in C vs. 1-indexing in R they where offset by one, thus, in flownet versions <= 0.1.2, the correct edge indices can be retained by subtracting 1 from them.
Improved Step 7 (elimination of path with duplicate edges) in the route enumeration algorithm to properly handle directed paths, i.e., candidate paths where an intermediate node is approached via an edge and departed from via the same edge but in a different direction, are now also removed.
Added option return.extra = "PSF" which adds "path_size_factors" to the results object. This should be useful to calibrate the PSL model.
Added option return.extra = "eweights" which adds "egde_weights" to the results object. Edge weights are the sum of the path probabilities across all paths using that edge. These weights are computed efficiently at C-level, with minimal overhead, if requested.
Added verbosity to simplify_network() (default verbose = TRUE).
Reordered elements in results object (class 'flownet') in a natural way: providing first the final flows, followed by path and edge-level additional results if requested through return.extra.
Added more unit tests covering return.extra options.
Added variable labels to included africa_* datasets - try collapse::namlab() on them.
Small improvements to recursive logic in consolidate_graph().
Bumped kit dependency to 0.0.21 (for fpmin() and fpmax()).
In consolidate_graph(): argument consolidate was renamed to contract for improved clarity, while ensuring backwards compatibility.
Minor improvements to documentation and vignette.
run_assignment() @details section using \subsection{} for better organization:
return.extra parameter documentation as a clear table showing which options are available for each methodpaths returns edge indices, not node indicesnthreads parameterrun_assignment() (AoN and PSL methods)normalize_graph(), nodes_from_graph(), distances_from_graph()linestrings_to_graph(), linestrings_from_graph(), create_undirected_graph()consolidate_graph(), simplify_network()melt_od_matrix()simplify_network() shortest-paths methodrun_assignment(): Core function for traffic assignment using the path-sized logit (PSL) model
mirai.linestrings_to_graph(): Convert LINESTRING geometries (sf objects) to graph data frames
create_undirected_graph(): Convert directed graphs to undirected graphs
collapse::collap() with customizable functionsconsolidate_graph(): Simplify network topology by removing intermediate nodes
simplify_network(): Simplify networks using shortest-paths or spatial clustering methods
leaderCluster algorithm and contracts the graphnormalize_graph(): Normalize node IDs to consecutive integers starting from 1
nodes_from_graph(): Extract unique nodes with coordinates from graph
linestrings_from_graph(): Convert graph data frames back to LINESTRING geometries
linestrings_to_graph()distances_from_graph(): Compute distance matrices for all node pairs
melt_od_matrix(): Convert origin-destination matrices to long format
africa_network: A road transport network with 2,825 LINESTRING features representing existing roads (2,344 edges) and proposed new links (481 edges). Each edge includes attributes such as distance, travel duration, border crossing costs, terrain ruggedness, and road upgrade costs.
africa_cities_ports: 453 African cities with population > 100,000 and international ports. Includes population data, capital status, and port cargo outflows.
africa_segments: 14,358 raw network segments representing intersected road routes. Useful for demonstrating network consolidation and simplification functions.
africa_trade: Bilateral trade flows between 47 African countries aggregated by HS section (21 product categories). Values represent annual averages over 2012-2022.
The africa_network, africa_cities_ports, and africa_segments datasets are from Krantz, S. (2024). Optimal Investments in Africa's Road Network. Policy Research Working Paper 10893. World Bank. Replication materials are available at github.com/SebKrantz/OptimalAfricanRoads.
collapse package for fast data transformationsigraph for graph operations and shortest path algorithmsgeodist for fast geodesic distance computationsleaderCluster for efficient spatial clustering?flownet-packageGPL-3