distance, the most common measure of great-circle spherical distance: $$dist_{ij} = haversine(lat_i,lon_i, lat_j,lon_j)$$

where the coordinate pairs for $i,j$ are of the places where those users have checked-in most frequently, equivalent to the mode in the multiset of venues where they have checked-in. We only consider users who have more than two check-ins over the whole period, and resolve ties by picking an arbitrary venue location from the top ranked venues of a user.

In Figures \[fig:men\] to \[fig:dist\], we observe four types of geographic and social interaction on the two social networking services, where each box-and-whiskers plot represents an interaction between multiplex links (*tf*), Twitter only (*to*), Foursquare only (*fo*), and unconnected pairs (*na*) on the x axis. On the y axis we can observe the distribution in four quartiles, representing 25% of values each. The dark line in the middle of the box represents the median of the distribution, while the dots are the outliers. The “whiskers" represent the top and bottom quartiles, while the boxes are the middle quartiles of the distribution.

In terms of Twitter mentions (Figure \[fig:men\]), multiplex ties and non-connected pairs of users exhibit an overall greater number of mentions than any other group, 