Figure 3
From: The geography and carbon footprint of mobile phone use in Cote d’Ivoire
Correlation between population and phone call intensity. (a) Scatter plot of the total number of outgoing calls versus the population. Both variables are counted on a 5 km × 5 km square grid. An ordinary least-squares fit yields different slopes for small and large populations. (b) The spatial autocorrelation functions for the number of calls and the population size exhibit significant non-zero correlations up to ≈15 km.