--- a/SmallWorldGraph.py	Thu Jan 03 18:41:13 2013 -0600
+++ b/SmallWorldGraph.py	Sat Jan 05 13:00:07 2013 -0600
@@ -127,12 +127,42 @@
                     queue.append(w)
                     sort_flag = True
 
+    def all_pairs_floyd_warshall(self):
+        """Finds the shortest paths between all pairs of vertices using the
+        Floyd-Warshall algorithm.
+
+        http://en.wikipedia.org/wiki/Floyd-Warshall_algorithm
+
+        """
+        vertices = self.vertices()
+        dist = {}
+        for i in vertices:
+            for j in vertices:
+                if i is j:
+                    dist[i, j] = 0.0
+                else:
+                    e = self.get_edge(i, j)
+                    dist[i, j] = e.length if e else INFINITY
+
+        for k in vertices:
+            for i in vertices:
+                for j in vertices:
+                    d_ik = dist[i, k]
+                    d_kj = dist[k, j]
+                    new_cost = d_ik + d_kj
+                    if new_cost < dist[i, j]:
+                        dist[i, j] = new_cost
+
+        return dist
+
     def big_l(self):
         """Computes the "big-L" value for the graph as per Watts & Strogatz.
 
         big_l() is defined as the number of edges in the shortest path between
         two vertices, averaged over all vertices.
 
+        Uses the shortest_path_tree() method, called once for every node.
+
         """
         d = {}
         for v in self.vertices():
@@ -143,3 +173,20 @@
         if len(d):
             return sum(d.values()) / float(len(d))
         return 0.0
+
+    def big_l2(self):
+        """Computes the "big-L" value for the graph as per Watts & Strogatz.
+
+        big_l() is defined as the number of edges in the shortest path between
+        two vertices, averaged over all vertices.
+
+        Uses the all_pairs_floyd_warshall() method.
+
+        """
+        dist = self.all_pairs_floyd_warshall()
+        vertices = self.vertices()
+        result = [dist[i, j] for i in vertices for j in vertices if i is not j]
+
+        if len(result):
+            return sum(result) / float(len(result))
+        return 0.0