Figure 2. The characteristic functions of human communication event sequences.

The P(E) distributions with various Δt time-window sizes (main panels), P(t_ie) distributions (left bottom panels) and average autocorrelation functions (right bottom panels) calculated for different communication datasets. (a) Mobile-call dataset: the scale-invariant behavior was characterized by power-law functions with exponent values , and (b) Almost the same exponents were estimated for short message sequences taking values , and . (c) Email event sequence with estimated exponents , and . A gap in the tail of A(τ) on figure (c) appears due to logarithmic binning and slightly negative correlation values. Empty symbols assign the corresponding calculation results on independent sequences. Lanes labeled with s, m, h and d are denoting seconds, minutes, hours and days respectively.