Partitioning of large European countries based on telephone call networks.

<p>Left column: Community detection (first level) of telephone call networks of (A) France, (C) UK, (E) Italy. The black lines show the 22, 11, and 20 administrative regions (NUTS1 for UK, NUTS2 for the other countries), respectively, the colored areas show the corresponding 21, 16, 22 level 1 regions found by applying the modularity optimization algorithm on the country-wide phone call networks. All detected regions are cohesive although some of the distinct colors used may appear similar. Right column: Community detection (second level) within all network partitions from the first level, of (B) France, (D) UK, (F) Italy. For visual clarity here we present the second level communities grouped into first level communities in an exploded view. Colors of detected subregions only apply inside their respective level 1 partitions, again all detected subregions are cohesive although some of the distinct colors used may appear similar. For France we also show the official NUTS2 borders which considerably match well the second level partitioning.