Fig 1. The diffusion trees in LJ community.

a, a real instance of information diffusion. An illustration of a diffusion tree containing 227 nodes which reaches the depth of 8. Each node represents a post published in LJ community, whereas each link stands for a spreading instance. The node color indicates the depth of a node in the diffusion tree. The size of a node is proportional to the number of its children. The links of social spreading, self-promotion, and broadcast are represented by the colors of red, grey, and blue respectively. b shows the probability distributions of diffusion trees’ size and depth. Both the tree size and depth exhibit approximately pow-law distributions. The power-law exponents for tree size and depth are γ _s = 1.86 ± 0.05 and γ _d = 2.97 ± 0.29 respectively. The straight lines represent the maximum likelihood fitting of the data points.