add: degree centrality

comparison.py

@@ -8,6 +8,16 @@ from src import centrality
 from src import plot
 from src import fitting
 
+
+def degree(g, weight):
+    # VertexPropertyMap
+    vp = g.new_vertex_property("double")
+    for v in g.vertices():
+        neighbours = g.get_all_neighbours(v)
+        vp[v] = len(neighbours)
+    return vp
+
+
 def leverage(g, weight):
     # VertexPropertyMap
     vp = g.new_vertex_property("double")