def incidents(self, node):
"""
overrides the incidents function of digraph, to maintain the nodes mapping
@type node: Node
@param node: the nodes of the neighbors
"""
if isinstance(node, Node):
return [self.nodesMap[uid] for uid in digraph.incidents(self, node.uid)]
else:
return digraph.incidents(self, node)
def page_rank(self):
'''计算有向图PR值
'''
# 初始化一些参量
digraph = self.digraph
nodes = digraph.nodes()
graph_size = len(nodes)
if graph_size == 0:
return {}
# 将没有出链节点添加和其他所有节点(包括自己)连接边
for node in nodes:
if len(digraph.neighbors(node))==0:
for linkNode in nodes:
digraph.add_edge((node, linkNode))
# 初始化PR值
PR = dict.fromkeys(nodes, 1/graph_size)
damping_value = (1-self.damping_factor)/graph_size
# 迭代
for i in range(self.max_iterations):
change = 0
# 遍历每个节点，求解PR值
for node in nodes:
rank = 0
for inciNode in digraph.incidents(node):
rank += self.damping_factor*PR[inciNode]/len(digraph.neighbors(inciNode))
rank += damping_value
change += abs(PR[node]-rank)
PR[node]=rank
# 判断是否终止
if change <= self.min_delta:
flag = True
break
if flag:
print("finished in %d iterations."%i)
else:
print("finished out of iterations")
return PR