feat: mean_degree()

CHANGELOG.md

@@ -4,6 +4,7 @@
 
  - Added `Graph.Chung_Lu()` for sampling from the Chung-Lu model as well as several related models.
  - Added `Graph.is_complete()` to test if there is a connection between all distinct pairs of vertices.
+ - Added `Graph.mean_degree()` for a convenient way to compute the average degree of a graph.
 
 ### Changed
 

src/_igraph/graphobject.c

@@ -962,6 +962,29 @@ PyObject *igraphmodule_Graph_density(igraphmodule_GraphObject * self,
   return igraphmodule_real_t_to_PyObject(res, IGRAPHMODULE_TYPE_FLOAT);
 }
 
+/** \ingroup python_interface_graph
+ * \brief Calculates the mean degree
+ * \return the mean degree
+ * \sa igraph_mean_degree
+ */
+PyObject *igraphmodule_Graph_mean_degree(igraphmodule_GraphObject * self,
+                                     PyObject * args, PyObject * kwds)
+{
+  char *kwlist[] = { "loops", NULL };
+  igraph_real_t res;
+  PyObject *loops = Py_True;
+
+  if (!PyArg_ParseTupleAndKeywords(args, kwds, "|O", kwlist, &loops))
+    return NULL;
+
+  if (igraph_mean_degree(&self->g, &res, PyObject_IsTrue(loops))) {
+    igraphmodule_handle_igraph_error();
+    return NULL;
+  }
+
+  return igraphmodule_real_t_to_PyObject(res, IGRAPHMODULE_TYPE_FLOAT);
+}
+
 /** \ingroup python_interface_graph
  * \brief The maximum degree of some vertices in an \c igraph.Graph
  * \return the maxium degree as a Python object
@@ -15075,6 +15098,14 @@ struct PyMethodDef igraphmodule_Graph_methods[] = {
    "  assumes that there can't be any loops.\n"
    "@return: the density of the graph."},
 
+  /* interface to igraph_mean_degree */
+  {"mean_degree", (PyCFunction) igraphmodule_Graph_mean_degree,
+   METH_VARARGS | METH_KEYWORDS,
+   "mean_degree(loops=True)\n--\n\n"
+   "Calculates the mean degree of the graph.\n\n"
+   "@param loops: whether to consider self-loops during the calculation\n"
+   "@return: the mean degree of the graph."},
+
   /* interfaces to igraph_diameter */
   {"diameter", (PyCFunction) igraphmodule_Graph_diameter,
    METH_VARARGS | METH_KEYWORDS,

tests/test_structural.py

@@ -24,6 +24,13 @@ def testDensity(self):
         self.assertAlmostEqual(7 / 16, self.gdir.density(True), places=5)
         self.assertAlmostEqual(1 / 7, self.tree.density(), places=5)
 
+    def testMeanDegree(self):
+        self.assertEqual(9.0, self.gfull.mean_degree())
+        self.assertEqual(0.0, self.gempty.mean_degree())
+        self.assertEqual(2.5, self.g.mean_degree())
+        self.assertEqual(7 / 4, self.gdir.mean_degree())
+        self.assertAlmostEqual(13 / 7, self.tree.mean_degree(), places=5)
+
     def testDiameter(self):
         self.assertTrue(self.gfull.diameter() == 1)
         self.assertTrue(self.gempty.diameter(unconn=False) == inf)