学位相关性在嵌套网络的四种类型。(一)r(,)意味着in-degree-in-degree相关性;(b)r(,)意味着in-degree-out-degree相关性;(c)r(在)意味着out-degree-in-degree相关性;(d)r(,)意味着out-degree-out-degree相关性。