Tracking urban human activity from mobile phone calling patterns
Fig 3
Time progression of the onset and termination of the calling activity along the geographical longitude.
Temporal progression of the onset and termination of the calling activity for cities lying at different geographical longitude. The time shift n*Δ that minimizes the divergence between the probability distribution of the first call PF in a reference city and the corresponding distributions of the other different cities lying at the same latitude. 4 different bands are analyzed, centred at 37.5°N, 39.5°N, 41.5°N, and +43.1°N. For each city inside each band, the time shifts n*Δ for the 7 days of the week are shown, as the set of 7 points with the same color located at the corresponding time difference between the local meridians of each city and that of the reference. The dashed line represents the time shift between the sun transit time at the reference city and a hypothetical point located at each corresponding longitude. The error bars represent the standard deviation from the average value for each day of the week. From the plot it can be seen that, for cities lying further away from the reference city, a bigger time shift is required to collapse the distributions.