Add connected_components, merge_vertices. Fix incident_edges.

Author: mtfishman

Project.toml

@@ -1,7 +1,7 @@
 name = "NamedGraphs"
 uuid = "678767b0-92e7-4007-89e4-4527a8725b19"
 authors = ["Matthew Fishman <[email protected]> and contributors"]
-version = "0.1.4"
+version = "0.1.5"
 
 [deps]
 AbstractTrees = "1520ce14-60c1-5f80-bbc7-55ef81b5835c"

src/Graphs/abstractgraph.jl

@@ -150,12 +150,44 @@ function is_tree(graph::AbstractGraph)
   return (ne(graph) == nv(graph) - 1) && is_connected(graph)
 end
 
-function incident_edges(graph::AbstractGraph, vertex)
+function out_incident_edges(graph::AbstractGraph, vertex)
   return [
-    edgetype(graph)(vertex, neighbor_vertex) for neighbor_vertex in neighbors(graph, vertex)
+    edgetype(graph)(vertex, neighbor_vertex) for neighbor_vertex in outneighbors(graph, vertex)
   ]
 end
 
+function in_incident_edges(graph::AbstractGraph, vertex)
+  return [
+    edgetype(graph)(neighbor_vertex, vertex) for neighbor_vertex in inneighbors(graph, vertex)
+  ]
+end
+
+function all_incident_edges(graph::AbstractGraph, vertex)
+  return out_incident_edges(graph, vertex) ∪ in_incident_edges(graph, vertex)
+end
+
+"""
+    incident_edges(graph::AbstractGraph, vertex; dir=:out)
+
+Edges incident to the vertex `vertex`.
+
+`dir ∈ (:in, :out, :both)`, defaults to `:out`.
+
+For undirected graphs, returns all incident edges.
+
+Like: https://juliagraphs.org/Graphs.jl/v1.7/algorithms/linalg/#Graphs.LinAlg.adjacency_matrix
+"""
+function incident_edges(graph::AbstractGraph, vertex; dir=:out)
+  if dir == :out
+    return out_incident_edges(graph, vertex)
+  elseif dir == :in
+    return in_incident_edges(graph, vertex)
+  elseif dir == :both
+    return all_incident_edges(graph, vertex)
+  end
+  return error("dir = $dir not supported.")
+end
+
 # Get the leaf vertices of a tree-like graph
 # 
 # For the directed case, could also use `AbstractTrees`:

src/NamedGraphs.jl

@@ -20,6 +20,8 @@ import Graphs:
   bfs_tree,
   blockdiag,
   common_neighbors,
+  connected_components,
+  connected_components!,
   degree,
   degree_histogram,
   dst,
@@ -38,6 +40,8 @@ import Graphs:
   is_directed,
   is_strongly_connected,
   is_weakly_connected,
+  merge_vertices,
+  merge_vertices!,
   ne,
   neighbors,
   neighborhood,

src/abstractnamedgraph.jl

@@ -12,6 +12,8 @@ parent_graph(graph::AbstractNamedGraph) = not_implemented()
 # ?
 parent_graph_type(graph::AbstractNamedGraph) = not_implemented()
 
+parent_vertextype(graph::AbstractNamedGraph) = vertextype(parent_graph(graph))
+
 # Convert vertex to parent vertex
 # Inverse map of `parent_vertex_to_vertex`.
 vertex_to_parent_vertex(graph::AbstractNamedGraph, vertex) = not_implemented()
@@ -83,12 +85,20 @@ function vertices_to_parent_vertices(
   return map(vertex_to_parent_vertex(graph), vertices)
 end
 
+function vertices_to_parent_vertices(graph::AbstractNamedGraph)
+  return Base.Fix1(vertices_to_parent_vertices, graph)
+end
+
 function parent_vertices_to_vertices(
   graph::AbstractNamedGraph, parent_vertices
 )
   return map(parent_vertex_to_vertex(graph), parent_vertices)
 end
 
+function parent_vertices_to_vertices(graph::AbstractNamedGraph)
+  return Base.Fix1(parent_vertices_to_vertices, graph)
+end
+
 parent_vertices(graph::AbstractNamedGraph) = vertices(parent_graph(graph))
 parent_edges(graph::AbstractNamedGraph) = edges(parent_graph(graph))
 parent_edgetype(graph::AbstractNamedGraph) = edgetype(parent_graph(graph))
@@ -378,6 +388,36 @@ function adjacency_matrix(graph::AbstractNamedGraph, args...)
   return adjacency_matrix(parent_graph(graph), args...)
 end
 
+function connected_components(graph::AbstractNamedGraph)
+  parent_connected_components = connected_components(parent_graph(graph))
+  return map(parent_vertices_to_vertices(graph), parent_connected_components)
+end
+
+function merge_vertices!(graph::AbstractNamedGraph, merge_vertices; merged_vertex=first(merge_vertices))
+  not_implemented()
+end
+
+function merge_vertices(graph::AbstractNamedGraph, merge_vertices; merged_vertex=first(merge_vertices))
+  merged_graph = copy(graph)
+  if !has_vertex(graph, merged_vertex)
+    add_vertex!(merged_graph, merged_vertex)
+  end
+  for vertex in merge_vertices
+    for e in incident_edges(graph, vertex; dir=:both)
+      merged_edge = rename_vertices(v -> v == vertex ? merged_vertex : v, e)
+      if src(merged_edge) ≠ dst(merged_edge)
+        add_edge!(merged_graph, merged_edge)
+      end
+    end
+  end
+  for vertex in merge_vertices
+    if vertex ≠ merged_vertex
+      rem_vertex!(merged_graph, vertex)
+    end
+  end
+  return merged_graph
+end
+
 # 
 # Graph traversals
 #

test/test_namedgraph.jl

@@ -63,6 +63,82 @@ end
     @test has_path(g, "D", "E")
     @test !has_path(g, "A", "E")
   end
+  @testset "neighborhood" begin
+    g = named_grid((4, 4))
+    @test issetequal(neighborhood(g, (1, 1), nv(g)), vertices(g))
+    @test issetequal(neighborhood(g, (1, 1), 0), [(1, 1)])
+    @test issetequal(neighborhood(g, (1, 1), 1), [(1, 1), (2, 1), (1, 2)])
+    ns = [
+      (1, 1),
+      (2, 1),
+      (1, 2),
+      (3, 1),
+      (2, 2),
+      (1, 3),
+    ]
+    @test issetequal(neighborhood(g, (1, 1), 2), ns)
+    ns = [
+      (1, 1),
+      (2, 1),
+      (1, 2),
+      (3, 1),
+      (2, 2),
+      (1, 3),
+      (4, 1),
+      (3, 2),
+      (2, 3),
+      (1, 4),
+    ]
+    @test issetequal(neighborhood(g, (1, 1), 3), ns)
+    ns = [
+      (1, 1),
+      (2, 1),
+      (1, 2),
+      (3, 1),
+      (2, 2),
+      (1, 3),
+      (4, 1),
+      (3, 2),
+      (2, 3),
+      (1, 4),
+      (4, 2),
+      (3, 3),
+      (2, 4),
+    ]
+    @test issetequal(neighborhood(g, (1, 1), 4), ns)
+    ns = [
+      (1, 1),
+      (2, 1),
+      (1, 2),
+      (3, 1),
+      (2, 2),
+      (1, 3),
+      (4, 1),
+      (3, 2),
+      (2, 3),
+      (1, 4),
+      (4, 2),
+      (3, 3),
+      (2, 4),
+      (4, 3),
+      (3, 4),
+    ]
+    @test issetequal(neighborhood(g, (1, 1), 5), ns)
+    @test issetequal(neighborhood(g, (1, 1), 6), vertices(g))
+    ns_ds = [
+      ((1, 1), 0),
+      ((2, 1), 1),
+      ((1, 2), 1),
+      ((3, 1), 2),
+      ((2, 2), 2),
+      ((1, 3), 2),
+      ((4, 1), 3),
+      ((3, 2), 3),
+      ((2, 3), 3),
+      ((1, 4), 3),
+    ]
+    @test issetequal(neighborhood_dists(g, (1, 1), 3), ns_ds)
+  end
   @testset "Basics (directed)" begin
     g = NamedDiGraph(["A", "B", "C", "D"])
     add_edge!(g, "A" => "B")
@@ -244,13 +320,123 @@ end
     )
       @test_broken f(g, "A")
     end
-  @testset "has_self_loops" begin
+  end
+  @testset "Graph connectivity" begin
     g = NamedGraph(2)
     @test g isa NamedGraph{Int}
     add_edge!(g, 1, 2)
     @test !has_self_loops(g)
     add_edge!(g, 1, 1)
     @test has_self_loops(g)
+
+    g1 = named_grid((2, 2))
+    g2 = named_grid((2, 2))
+    g = g1 ⊔ g2
+    t = named_binary_tree(3)
+
+    @test is_cyclic(g1)
+    @test is_cyclic(g2)
+    @test is_cyclic(g)
+    @test !is_cyclic(t)
+
+    @test is_connected(g1)
+    @test is_connected(g2)
+    @test !is_connected(g)
+    @test is_connected(t)
+
+    cc = connected_components(g1)
+    @test length(cc) == 1
+    @test length(only(cc)) == nv(g1)
+    @test issetequal(only(cc), vertices(g1))
+
+    cc = connected_components(g)
+    @test length(cc) == 2
+    @test length(cc[1]) == nv(g1)
+    @test length(cc[2]) == nv(g2)
+    @test issetequal(cc[1], map(v -> (v, 1), vertices(g1)))
+    @test issetequal(cc[2], map(v -> (v, 2), vertices(g2)))
+  end
+  @testset "incident_edges" begin
+    g = grid((3, 3))
+    inc_edges = Edge.([2 => 1, 2 => 3, 2 => 5])
+    @test issetequal(incident_edges(g, 2), inc_edges)
+    @test issetequal(incident_edges(g, 2; dir=:in), reverse.(inc_edges))
+    @test issetequal(incident_edges(g, 2; dir=:out), inc_edges)
+    @test issetequal(incident_edges(g, 2; dir=:both), inc_edges ∪ reverse.(inc_edges))
+
+    g = named_grid((3, 3))
+    inc_edges = NamedEdge.([
+      (2, 1) => (1, 1),
+      (2, 1) => (3, 1),
+      (2, 1) => (2, 2),
+    ])
+    @test issetequal(incident_edges(g, (2, 1)), inc_edges)
+    @test issetequal(incident_edges(g, (2, 1); dir=:in), reverse.(inc_edges))
+    @test issetequal(incident_edges(g, (2, 1); dir=:out), inc_edges)
+    @test issetequal(incident_edges(g, (2, 1); dir=:both), inc_edges ∪ reverse.(inc_edges))
+
+    g = path_digraph(4)
+    @test issetequal(incident_edges(g, 3), Edge.([3 => 4]))
+    @test issetequal(incident_edges(g, 3; dir=:in), Edge.([2 => 3]))
+    @test issetequal(incident_edges(g, 3; dir=:out), Edge.([3 => 4]))
+    @test issetequal(incident_edges(g, 3; dir=:both), Edge.([2 => 3, 3 => 4]))
+
+    g = NamedDiGraph(path_digraph(4), ["A", "B", "C", "D"])
+    @test issetequal(incident_edges(g, "C"), NamedEdge.(["C" => "D"]))
+    @test issetequal(incident_edges(g, "C"; dir=:in), NamedEdge.(["B" => "C"]))
+    @test issetequal(incident_edges(g, "C"; dir=:out), NamedEdge.(["C" => "D"]))
+    @test issetequal(incident_edges(g, "C"; dir=:both), NamedEdge.(["B" => "C", "C" => "D"]))
   end
+  @testset "merge_vertices" begin
+    g = named_grid((3, 3))
+    mg = merge_vertices(g, [(2, 2), (2, 3), (3, 3)])
+    @test nv(mg) == 7
+    @test ne(mg) == 9
+    merged_vertices = [
+      (1, 1),
+      (2, 1),
+      (3, 1),
+      (1, 2),
+      (2, 2),
+      (3, 2),
+      (1, 3),
+    ]
+    for v in merged_vertices
+      @test has_vertex(mg, v)
+    end
+    merged_edges = [
+      (1, 1) => (2, 1),
+      (1, 1) => (1, 2),
+      (2, 1) => (3, 1),
+      (2, 1) => (2, 2),
+      (3, 1) => (3, 2),
+      (1, 2) => (2, 2),
+      (1, 2) => (1, 3),
+      (2, 2) => (3, 2),
+      (2, 2) => (1, 3),
+    ]
+    for e in merged_edges
+      @test has_edge(mg, e)
+    end
+
+    sg = SimpleDiGraph(4)
+    g = NamedDiGraph(sg, ["A", "B", "C", "D"])
+    add_edge!(g, "A" => "B")
+    add_edge!(g, "B" => "C")
+    add_edge!(g, "C" => "D")
+    mg = merge_vertices(g, ["B", "C"])
+    @test ne(mg) == 2
+    @test has_edge(mg, "A" => "B")
+    @test has_edge(mg, "B" => "D")
+
+    sg = SimpleDiGraph(4)
+    g = NamedDiGraph(sg, ["A", "B", "C", "D"])
+    add_edge!(g, "B" => "A")
+    add_edge!(g, "C" => "B")
+    add_edge!(g, "D" => "C")
+    mg = merge_vertices(g, ["B", "C"])
+    @test ne(mg) == 2
+    @test has_edge(mg, "B" => "A")
+    @test has_edge(mg, "D" => "B")
   end
 end