feat: add make_wheel() to expose igraph_wheel() (#2409)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: krlmlr <[email protected]>
Co-authored-by: Kirill Müller <[email protected]>

Author: Copilot

NAMESPACE

@@ -674,6 +674,7 @@ export(make_star)
 export(make_tree)
 export(make_turan)
 export(make_undirected_graph)
+export(make_wheel)
 export(match_vertices)
 export(max_bipartite_match)
 export(max_cardinality)
@@ -902,6 +903,7 @@ export(walktrap.community)
 export(watts.strogatz.game)
 export(weighted_clique_num)
 export(weighted_cliques)
+export(wheel)
 export(which_loop)
 export(which_multiple)
 export(which_mutual)

R/make.R

@@ -2071,6 +2071,70 @@ ring <- function(...) constructor_spec(make_ring, ...)
 
 ## -----------------------------------------------------------------
 
+#' Create a wheel graph
+#'
+#' @description
+#' `r lifecycle::badge("experimental")`
+#'
+#' A wheel graph is created by connecting a center vertex to all vertices of a
+#' cycle graph.
+#' A wheel graph on `n` vertices can be thought of as a wheel with `n - 1`
+#' spokes.
+#' The cycle graph part makes up the rim, while the star graph part adds the
+#' spokes.
+#'
+#' Note that the two and three-vertex wheel graphs are non-simple: The
+#' two-vertex wheel graph contains a self-loop, while the three-vertex wheel
+#' graph contains parallel edges (a 1-cycle and a 2-cycle, respectively).
+#'
+#' @concept Wheel graph
+#' @param n Number of vertices.
+#' @inheritParams rlang::args_dots_empty
+#' @param mode It defines the direction of the edges.
+#'   `in`: the edges point *to* the center, `out`: the edges point *from* the
+#'   center, `mutual`: a directed wheel is created with mutual edges,
+#'   `undirected`: the edges are undirected.
+#' @param center ID of the center vertex.
+#' @return An igraph graph.
+#'
+#' @family deterministic constructors
+#' @export
+#' @examples
+#' make_wheel(10, mode = "out")
+#' make_wheel(5, mode = "undirected")
+#' @cdocs igraph_wheel
+make_wheel <- function(
+  n,
+  ...,
+  mode = c("in", "out", "mutual", "undirected"),
+  center = 1
+) {
+  check_dots_empty()
+  res <- wheel_impl(
+    n = n,
+    mode = mode,
+    center = center - 1
+  )
+  if (igraph_opt("add.params")) {
+    res$name <- switch(
+      igraph_match_arg(mode),
+      "in" = "In-wheel",
+      "out" = "Out-wheel",
+      "Wheel"
+    )
+    res$mode <- mode
+    res$center <- center
+  }
+  res
+}
+
+#' @rdname make_wheel
+#' @param ... Passed to `make_wheel()`.
+#' @export
+wheel <- function(...) constructor_spec(make_wheel, ...)
+
+## -----------------------------------------------------------------
+
 #' Create tree graphs
 #'
 #' Create a k-ary tree graph, where almost all vertices other than the leaves