Added s parameter to neighbors

tests/core/test_views.py

@@ -5,11 +5,10 @@
 from xgi.exception import IDNotFound, XGIError
 
 
-def test_neighbors(edgelist1, edgelist2):
-    el1 = edgelist1
-    el2 = edgelist2
-    H1 = xgi.Hypergraph(el1)
-    H2 = xgi.Hypergraph(el2)
+def test_neighbors(edgelist1, edgelist2, edgelist7):
+    H1 = xgi.Hypergraph(edgelist1)
+    H2 = xgi.Hypergraph(edgelist2)
+    H3 = xgi.Hypergraph(edgelist7)
     assert H1.nodes.neighbors(1) == {2, 3}
     assert H1.nodes.neighbors(4) == set()
     assert H1.nodes.neighbors(6) == {5, 7, 8}
@@ -20,6 +19,10 @@ def test_neighbors(edgelist1, edgelist2):
     assert H1.edges.neighbors(1) == set()
     assert H1.edges.neighbors(2) == {3}
     assert H1.edges.neighbors(3) == {2}
+    assert H3.edges.neighbors(0, s=2) == {1}
+    assert H3.edges.neighbors(1, s=2) == {0, 2}
+    assert H3.edges.neighbors(2, s=2) == {1}
+    assert H3.edges.neighbors(3, s=2) == set()
 
 
 def test_edge_order(edgelist3):

xgi/core/views.py

@@ -330,7 +330,7 @@ def filterby_attr(self, attr, val, mode="eq", missing=None):
             )
         return type(self).from_view(self, bunch)
 
-    def neighbors(self, id):
+    def neighbors(self, id, s=1):
         """Find the neighbors of an ID.
 
         The neighbors of an ID are those IDs that share at least one bipartite ID.
@@ -339,6 +339,10 @@ def neighbors(self, id):
         ----------
         id : hashable
             ID to find neighbors of.
+        s : int, optional
+            The intersection size s for two edges or nodes to be considered neighbors.
+            By default, 1.
+
         Returns
         -------
         set
@@ -359,9 +363,17 @@ def neighbors(self, id):
         {1, 3, 4}
 
         """
-        return {i for n in self._id_dict[id] for i in self._bi_id_dict[n]}.difference(
-            {id}
-        )
+        if s == 1:
+            return {
+                i for n in self._id_dict[id] for i in self._bi_id_dict[n]
+            }.difference({id})
+        else:
+            return {
+                i
+                for n in self._id_dict[id]
+                for i in self._bi_id_dict[n]
+                if len(self._id_dict[id].intersection(self._id_dict[i])) >= s
+            }.difference({id})
 
     def duplicates(self):
         """Find IDs that have a duplicate.