Define subgraph for PartitionsGraphView (#106)

Author: mtfishman

Project.toml

@@ -1,7 +1,7 @@
 name = "NamedGraphs"
 uuid = "678767b0-92e7-4007-89e4-4527a8725b19"
 authors = ["Matthew Fishman <mfishman@flatironinstitute.org>, Joseph Tindall <jtindall@flatironinstitute.org> and contributors"]
-version = "0.7.0"
+version = "0.7.1"
 
 [deps]
 AbstractTrees = "1520ce14-60c1-5f80-bbc7-55ef81b5835c"

src/lib/GraphsExtensions/src/trees_and_forests.jl

@@ -48,15 +48,17 @@ end
 function forest_cover(g::AbstractGraph; spanning_tree=spanning_tree)
   edges_collected = edgetype(g)[]
   remaining_edges = edges(g)
+  g_reduced = rem_edges(g, edges_collected)
   forests = typeof(g)[]
   while !isempty(remaining_edges)
-    g_reduced = rem_edges(g, edges_collected)
     g_reduced_spanning_forest = spanning_forest(g_reduced; spanning_tree)
-    push!(edges_collected, edges(g_reduced_spanning_forest)...)
-    push!(forests, g_reduced_spanning_forest)
-    setdiff!(remaining_edges, edges(g_reduced_spanning_forest))
+    edges_collected = [edges_collected; collect(edges(g_reduced_spanning_forest))]
+    g_reduced = rem_edges(g, edges_collected)
+    forests = [forests; [g_reduced_spanning_forest]]
+    remaining_edges = setdiff(remaining_edges, edges(g_reduced_spanning_forest))
   end
-  return forests
+  # Narrow the element type if possible.
+  return identity.(forests)
 end
 
 # TODO: Define in `NamedGraphs.PartitionedGraphs`.

src/lib/PartitionedGraphs/src/partitionsgraphview.jl

@@ -19,10 +19,11 @@ for f in [
   :(Graphs.edges),
   :(Graphs.vertices),
   :(Graphs.rem_vertex!),
+  :(NamedGraphs.edgetype),
+  :(NamedGraphs.namedgraph_induced_subgraph),
+  :(NamedGraphs.ordered_vertices),
   :(NamedGraphs.position_graph),
   :(NamedGraphs.vertex_positions),
-  :(NamedGraphs.ordered_vertices),
-  :(NamedGraphs.edgetype),
   :(NamedGraphs.vertextype),
 ]
   @eval begin

test/test_partitionedgraph.jl

@@ -23,6 +23,7 @@ using NamedGraphs.GraphsExtensions:
   add_vertices!,
   boundary_edges,
   default_root_vertex,
+  edgetype,
   forest_cover,
   is_path_graph,
   is_self_loop,
@@ -72,6 +73,8 @@ using Test: @test, @testset
   @test edges(pgv) == parent.(partitionedges(pg))
   @test is_tree(pgv) == true
   @test neighbors(pgv, 1) == [2]
+  @test issetequal(vertices(subgraph(pgv, [2, 3, 4])), [2, 3, 4])
+  @test issetequal(edges(subgraph(pgv, [2, 3, 4])), edgetype(pgv).([2 => 3, 3 => 4]))
 
   #Same partitioning but with a dictionary constructor
   partition_dict = Dictionary([first(partition) for partition in partitions], partitions)