Fig. 7

Reticulation mechanisms of network growth among users (red points represent new link creation, and green points represent edge reinforcement). The x and y axes in these three figures are in logarithmic scale with a base of 10. The x-axis represents the in-degrees of online users in the past 24 h, and the y-axis represents the number of links created or strengthened in the next 24 h. Because the duration of each period is 72 h, two data sets are plotted in each figure (with the same color): in-degrees from hour 0 to 24 versus the number of link creations from hour 24 to 48; and in-degrees from hour 24 to 48 versus the number of link creations from hour 48 to 72. In addition, we measure two types of link creations: new links created (red dots); and link reinforcement (green dots)