UrbanAnalyst · harrysroberts · Oct 21, 2025 · Oct 30, 2025 · Oct 31, 2025 · Oct 31, 2025
diff --git a/DESCRIPTION b/DESCRIPTION
@@ -8,12 +8,16 @@ Authors@R: c(
     person("Robin", "Lovelace", role = "ctb"),
     person("Andrew", "Smith", role = "ctb"),
     person("Malcolm", "Morgan", role = "ctb"),
-    person("Andrea", "Gilardi", role="ctb", comment = c(ORCID = "0000-0002-9424-7439")),
-    person("Eduardo", "Leoni", role="ctb", comment = c(ORCID = "0000-0003-0955-5232")),
+    person("Andrea", "Gilardi", role = "ctb",
+           comment = c(ORCID = "0000-0002-9424-7439")),
+    person("Eduardo", "Leoni", role = "ctb",
+           comment = c(ORCID = "0000-0003-0955-5232")),
     person("Shane", "Saunders", role = "cph",
            comment = "Original author of included code for priority heaps"),
     person("Stanislaw", "Adaszewski", role = "cph",
-           comment = "author of include concaveman-cpp code") 
+           comment = "author of include concaveman-cpp code"),
+    person("Harry", "Roberts", , "ts22hr@leeds.ac.uk", role = "ctb",
+           comment = c(ORCID = "0009-0005-5443-0684"))
   )
 Description: Distances on dual-weighted directed graphs using
     priority-queue shortest paths (Padgham (2019) <doi:10.32866/6945>).
@@ -63,5 +67,5 @@ Encoding: UTF-8
 LazyData: true
 NeedsCompilation: yes
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.3.2
+RoxygenNote: 7.3.3
 SystemRequirements: GNU make
diff --git a/NEWS.md b/NEWS.md
@@ -6,6 +6,8 @@
 - Add `pairwise` parameter to `dodgr_times()`; thanks to @leoniedu (#314)
 - Fix bug with categorical distances that neglected edges through compound junctions (#305)
 - Fix bug in duplicating bi-directional edges in weighted sc-class graphs
+- Added support for strong components in `dodgr_components()` (#322)
+- Added Harry Roberts as a contributor
 
 ---
 

diff --git a/R/RcppExports.R b/R/RcppExports.R
@@ -213,7 +213,7 @@ rcpp_merge_cols <- function (graph) {
 #' in \code{sample_one_vertex}
 #'
 #' @param edge_map edge_map
-#' @return std::vector of 2 elements: [0] with value of largest connected
+#' @return std::vector of 2 elements: [0] with value of largest connected 
 #' component; [1] with random index to one edge that is part of that component.
 #' @noRd
 NULL
@@ -263,7 +263,35 @@ NULL
 #' identify_graph_components
 #'
 #' Identify initial graph components for each **vertex**
-#' Identification for edges is subsequently perrformed with
+#' Identification for edges is subsequently performed with 
+#' \code{rcpp_get_component_vector}.
+#'
+#' @param v unordered_map <vertex_id_t, vertex_t>
+#' @param com component map from each vertex to component numbers
+#' @noRd
+NULL
+
+#' strong_connect
+#'
+#' Helper function for applying Tarjan's algroithm to identify
+#' strong components recursively
+#'
+#' @param vt id of vertex currently being evaluated
+#' @param v unordered_map <vertex_id_t, vertex_t>
+#' @param com component map from each vertex to component numbers
+#' @param index_map map from each vertex to index number
+#' @param lowlink_map map from each vertex to lowlink number
+#' @param on_stack set of all vertices currently on stack
+#' @param s stack used to execute algorithm
+#' @param index used to execute algoritm
+#' @param compnum the current component number
+#' @noRd
+NULL
+
+#' identify_graph_strong_components
+#'
+#' Identify initial graph strong components for each **vertex**
+#' Identification for edges is subsequently performed with 
 #' \code{rcpp_get_component_vector}.
 #'
 #' @param v unordered_map <vertex_id_t, vertex_t>
@@ -278,11 +306,14 @@ NULL
 #' @param graph graph to be processed; stripped down and standardised to five
 #' columns
 #'
+#' @param strong A Boolean flag to indicate whether components should be strong,
+#' i.e. its vertices connected bidirectionally. Defaults to FALSE.
+#'
 #' @return Two vectors: one of edge IDs and one of corresponding component
 #' numbers
 #' @noRd
-rcpp_get_component_vector <- function (graph) {
-    .Call (`_dodgr_rcpp_get_component_vector`, graph)
+rcpp_get_component_vector <- function (graph, strong = FALSE) {
+    .Call (`_dodgr_rcpp_get_component_vector`, graph, strong)
 }
 
 #' rcpp_unique_rownames
@@ -484,4 +515,4 @@ rcpp_sf_as_network <- function (sf_lines, pr) {
 #' @noRd
 rcpp_route_times <- function (graph, left_side, turn_penalty) {
     .Call (`_dodgr_rcpp_route_times`, graph, left_side, turn_penalty)
-}
+}
diff --git a/R/graph-functions.R b/R/graph-functions.R
@@ -310,14 +310,16 @@ dodgr_vertices_internal <- function (graph) {
 #' column to `data.frame`.
 #'
 #' @param graph A `data.frame` of edges
+#' @param strong A Boolean flag to indicate whether components should be strong,
+#' i.e. its vertices connected bidirectionally. Defaults to FALSE.
 #' @return Equivalent graph with additional `component` column,
 #' sequentially numbered from 1 = largest component.
 #' @family modification
 #' @export
 #' @examples
 #' graph <- weight_streetnet (hampi)
 #' graph <- dodgr_components (graph)
-dodgr_components <- function (graph) {
+dodgr_components <- function (graph, strong = FALSE) {
 
     graph <- tbl_to_df (graph)
 
@@ -329,15 +331,17 @@ dodgr_components <- function (graph) {
         if (is.na (gr_cols$edge_id)) {
             graph2$edge_id <- seq_len (nrow (graph2))
         }
-        cns <- rcpp_get_component_vector (graph2)
-
+        cns <- rcpp_get_component_vector (graph2,strong)
+        
         indx <- match (graph2$edge_id, cns$edge_id)
         component <- cns$edge_component [indx]
+
+        # Handle where component numbers contain gaps using frequencies
         # Then re-number in order to decreasing component size:
-        graph$component <- match (
-            component,
-            order (table (component), decreasing = TRUE)
-        )
+        freqs <- table (component)
+        sorted_components <- names (freqs) [order (freqs, decreasing = TRUE)]
+        graph$component <- match (as.character (component), sorted_components)
+
     }
 
     return (graph)

diff --git a/codemeta.json b/codemeta.json
@@ -4,20 +4,17 @@
   "identifier": "dodgr",
   "description": "Distances on dual-weighted directed graphs using priority-queue shortest paths (Padgham (2019) <doi:10.32866/6945>). Weighted directed graphs have weights from A to B which may differ from those from B to A. Dual-weighted directed graphs have two sets of such weights. A canonical example is a street network to be used for routing in which routes are calculated by weighting distances according to the type of way and mode of transport, yet lengths of routes must be calculated from direct distances.",
   "name": "dodgr: Distances on Directed Graphs",
-  "relatedLink": [
-    "https://UrbanAnalyst.github.io/dodgr/",
-    "https://CRAN.R-project.org/package=dodgr"
-  ],
+  "relatedLink": ["https://UrbanAnalyst.github.io/dodgr/", "https://CRAN.R-project.org/package=dodgr"],
   "codeRepository": "https://github.com/UrbanAnalyst/dodgr",
   "issueTracker": "https://github.com/UrbanAnalyst/dodgr/issues",
   "license": "https://spdx.org/licenses/GPL-3.0",
-  "version": "0.4.3.015",
+  "version": "0.4.3.15",
   "programmingLanguage": {
     "@type": "ComputerLanguage",
     "name": "R",
     "url": "https://r-project.org"
   },
-  "runtimePlatform": "R version 4.5.1 (2025-06-13)",
+  "runtimePlatform": "R version 4.5.1 (2025-06-13 ucrt)",
   "provider": {
     "@id": "https://cran.r-project.org",
     "@type": "Organization",
@@ -69,6 +66,13 @@
       "givenName": "Eduardo",
       "familyName": "Leoni",
       "@id": "https://orcid.org/0000-0003-0955-5232"
+    },
+    {
+      "@type": "Person",
+      "givenName": "Harry",
+      "familyName": "Roberts",
+      "email": "ts22hr@leeds.ac.uk",
+      "@id": "https://orcid.org/0009-0005-5443-0684"
     }
   ],
   "copyrightHolder": [
@@ -362,7 +366,7 @@
     },
     "SystemRequirements": "GNU make"
   },
-  "fileSize": "37019.613KB",
+  "fileSize": "72585.397KB",
   "citation": [
     {
       "@type": "ScholarlyArticle",
@@ -381,10 +385,7 @@
         "@type": "PublicationIssue",
         "datePublished": "2019",
         "isPartOf": {
-          "@type": [
-            "PublicationVolume",
-            "Periodical"
-          ],
+          "@type": ["PublicationVolume", "Periodical"],
           "name": "Transport Findings"
         }
       }

diff --git a/man/dodgr_components.Rd b/man/dodgr_components.Rd
diff --git a/src/RcppExports.cpp b/src/RcppExports.cpp
@@ -190,13 +190,14 @@ BEGIN_RCPP
 END_RCPP
 }
 // rcpp_get_component_vector
-Rcpp::List rcpp_get_component_vector(const Rcpp::DataFrame& graph);
-RcppExport SEXP _dodgr_rcpp_get_component_vector(SEXP graphSEXP) {
+Rcpp::List rcpp_get_component_vector(const Rcpp::DataFrame& graph, bool strong);
+RcppExport SEXP _dodgr_rcpp_get_component_vector(SEXP graphSEXP, SEXP strongSEXP) {
 BEGIN_RCPP
     Rcpp::RObject rcpp_result_gen;
     Rcpp::RNGScope rcpp_rngScope_gen;
     Rcpp::traits::input_parameter< const Rcpp::DataFrame& >::type graph(graphSEXP);
-    rcpp_result_gen = Rcpp::wrap(rcpp_get_component_vector(graph));
+    Rcpp::traits::input_parameter< bool >::type strong(strongSEXP);
+    rcpp_result_gen = Rcpp::wrap(rcpp_get_component_vector(graph, strong));
     return rcpp_result_gen;
 END_RCPP
 }
@@ -441,7 +442,7 @@ static const R_CallMethodDef CallEntries[] = {
     {"_dodgr_rcpp_contract_graph", (DL_FUNC) &_dodgr_rcpp_contract_graph, 2},
     {"_dodgr_rcpp_merge_cols", (DL_FUNC) &_dodgr_rcpp_merge_cols, 1},
     {"_dodgr_rcpp_sample_graph", (DL_FUNC) &_dodgr_rcpp_sample_graph, 2},
-    {"_dodgr_rcpp_get_component_vector", (DL_FUNC) &_dodgr_rcpp_get_component_vector, 1},
+    {"_dodgr_rcpp_get_component_vector", (DL_FUNC) &_dodgr_rcpp_get_component_vector, 2},
     {"_dodgr_rcpp_unique_rownames", (DL_FUNC) &_dodgr_rcpp_unique_rownames, 3},
     {"_dodgr_rcpp_points_index_par", (DL_FUNC) &_dodgr_rcpp_points_index_par, 2},
     {"_dodgr_rcpp_points_to_edges_par", (DL_FUNC) &_dodgr_rcpp_points_to_edges_par, 2},

diff --git a/src/dodgr.dll b/src/dodgr.dll