Network analysis of an online community

We empirically study various network properties of an online community. The numbers of articles written by each user to the bulletin boards of each of the others are used to construct the directed and weighted network BB, and gifting behaviors among users are also kept track of, to build the network GG which is again directed and weighted. Detailed analysis reveals that BB and GG have very different network properties. In particular, whereas BB contains many more bidirectional links than directed arcs, GG shows the opposite characteristic. The number of writings on bulletin boards is found to decay with the distance from the hub vertex, which reflects the structural assortativeness in BB. We also observe that the activities in writings and purchases are negatively correlated with each other for highly active users in BB.