[GNNGraphs] implement remove_edges(g, p) (#474)

* new drop edge

* fix

* Update GNNGraphs/src/transform.jl

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

* Update GNNGraphs/src/transform.jl

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

---------

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

Author: rbSparky

GNNGraphs/src/transform.jl

@@ -151,12 +151,14 @@ end
 
 """
     remove_edges(g::GNNGraph, edges_to_remove::AbstractVector{<:Integer})
+    remove_edges(g::GNNGraph, p=0.5)
 
-Remove specified edges from a GNNGraph.
+Remove specified edges from a GNNGraph, either by specifying edge indices or by randomly removing edges with a given probability.
 
 # Arguments
 - `g`: The input graph from which edges will be removed.
-- `edges_to_remove`: Vector of edge indices to be removed.
+- `edges_to_remove`: Vector of edge indices to be removed. This argument is only required for the first method.
+- `p`: Probability of removing each edge. This argument is only required for the second method and defaults to 0.5.
 
 # Returns
 A new GNNGraph with the specified edges removed.
@@ -178,6 +180,14 @@ julia> g_new
 GNNGraph:
   num_nodes: 3
   num_edges: 4
+
+# Remove edges with a probability of 0.5
+julia> g_new = remove_edges(g, 0.5);
+
+julia> g_new
+GNNGraph:
+  num_nodes: 3
+  num_edges: 2
 ```
 """
 function remove_edges(g::GNNGraph{<:COO_T}, edges_to_remove::AbstractVector{<:Integer})
@@ -200,6 +210,13 @@ function remove_edges(g::GNNGraph{<:COO_T}, edges_to_remove::AbstractVector{<:In
              g.ndata, edata, g.gdata)
 end
 
+
+function remove_edges(g::GNNGraph{<:COO_T}, p = 0.5)
+    num_edges = g.num_edges
+    edges_to_remove = filter(_ -> rand() < p, 1:num_edges)        
+    return remove_edges(g, edges_to_remove)
+end
+
 """
     remove_multi_edges(g::GNNGraph; aggr=+)
 

GNNGraphs/test/transform.jl

@@ -126,6 +126,13 @@ end
         @test new_t == [4]
         @test new_w == [0.3]
         @test new_edata == ['c']
+
+        # drop with probability
+        gnew = remove_edges(g, Float32(1.0))
+        @test gnew.num_edges == 0
+
+        gnew = remove_edges(g, Float32(0.0))
+        @test gnew.num_edges == g.num_edges
     end
 end