Added remove_edges function (#414)

* added remove edge function

* tests

* added remove edge function

* fix

* fix

* fix

* fix

* fix

* Update src/GNNGraphs/transform.jl

Co-authored-by: Carlo Lucibello <[email protected]>

* Update src/GNNGraphs/transform.jl

Co-authored-by: Carlo Lucibello <[email protected]>

* Update transform.jl

* tests final

* Update Project.toml

* Update src/GNNGraphs/transform.jl

Co-authored-by: Carlo Lucibello <[email protected]>

* done

* fixes

* more tests

---------

Co-authored-by: Carlo Lucibello <[email protected]>

Author: rbSparky

.gitignore

@@ -8,5 +8,4 @@ Manifest.toml
 /docs/build/
 .vscode
 LocalPreferences.toml
-.DS_Store
-/test.jl
+.DS_Store

src/GNNGraphs/GNNGraphs.jl

@@ -72,6 +72,7 @@ export add_nodes,
        negative_sample,
        rand_edge_split,
        remove_self_loops,
+       remove_edges, 
        remove_multi_edges,
        set_edge_weight,
        to_bidirected,

src/GNNGraphs/transform.jl

@@ -149,6 +149,57 @@ function remove_self_loops(g::GNNGraph{<:ADJMAT_T})
              g.ndata, g.edata, g.gdata)
 end
 
+"""
+    remove_edges(g::GNNGraph, edges_to_remove::AbstractVector{<:Integer})
+
+Remove specified edges from a GNNGraph.
+
+# Arguments
+- `g`: The input graph from which edges will be removed.
+- `edges_to_remove`: Vector of edge indices to be removed.
+
+# Returns
+A new GNNGraph with the specified edges removed.
+
+# Example
+```julia
+julia> using GraphNeuralNetworks
+
+# Construct a GNNGraph
+julia> g = GNNGraph([1, 1, 2, 2, 3], [2, 3, 1, 3, 1])
+GNNGraph:
+  num_nodes: 3
+  num_edges: 5
+  
+# Remove the second edge
+julia> g_new = remove_edges(g, [2]);
+
+julia> g_new
+GNNGraph:
+  num_nodes: 3
+  num_edges: 4
+```
+"""
+function remove_edges(g::GNNGraph{<:COO_T}, edges_to_remove::AbstractVector{<:Integer})
+    s, t = edge_index(g)
+    w = get_edge_weight(g)
+    edata = g.edata
+
+    mask_to_keep = trues(length(s))
+
+    mask_to_keep[edges_to_remove] .= false
+
+    s = s[mask_to_keep]
+    t = t[mask_to_keep]
+    edata = getobs(edata, mask_to_keep)
+    w = isnothing(w) ? nothing : getobs(w, mask_to_keep)
+
+    return GNNGraph((s, t, w),
+             g.num_nodes, length(s), g.num_graphs,
+             g.graph_indicator,
+             g.ndata, edata, g.gdata)
+end
+
 """
     remove_multi_edges(g::GNNGraph; aggr=+)
 

test/GNNGraphs/transform.jl

@@ -101,6 +101,34 @@ end
     @test nodemap == 1:(g1.num_nodes)
 end
 
+@testset "remove_edges" begin
+    if GRAPH_T == :coo
+        s = [1, 1, 2, 3]
+        t = [2, 3, 4, 5]
+        w = [0.1, 0.2, 0.3, 0.4]
+        edata = ['a', 'b', 'c', 'd']
+        g = GNNGraph(s, t, w, edata = edata, graph_type = GRAPH_T)    
+
+        # single edge removal
+        gnew = remove_edges(g, [1])
+        new_s, new_t = edge_index(gnew)
+        @test gnew.num_edges == 3
+        @test new_s == s[2:end]
+        @test new_t == t[2:end]
+        
+        # multiple edge removal
+        gnew = remove_edges(g, [1,2,4])
+        new_s, new_t = edge_index(gnew)
+        new_w = get_edge_weight(gnew)
+        new_edata = gnew.edata.e
+        @test gnew.num_edges == 1
+        @test new_s == [2]
+        @test new_t == [4]
+        @test new_w == [0.3]
+        @test new_edata == ['c']
+    end
+end
+
 @testset "add_edges" begin 
     if GRAPH_T == :coo
         s = [1, 1, 2, 3]