Cumulative distribution function (CDF) of the distance from Foursquare users' top locations to a check-in venue.

<p>Top locations are the locations where a user has checked in the most in the past. ‘Closer’ refers to the distance to the closest of a pair of users' top locations in a colocation event, ‘mean’ refers to the mean distance to the users' top locations, and ‘single’ is the function for all check-ins, not just ‘social’ check-ins that make up colocations between friends. Social check-ins tend to take place closer to a top location of one of a pair of colocated friends than do general check-ins to a top location of the checking-in user.</p

Cumulative distribution function (CDF) of the distance from cellphone users' top locations to a group colocation venue.

<p>Top locations are the locations where a user has made or received a phone call the most in the past. ‘Closer’ refers to the distance to the closest of a user's top locations in a colocation event, ‘mean’ refers to the mean distance to the user's top locations, and ‘single’ is the function for all calls, not just colocations. Groups tend to congregate closer to their members' top locations than people tend to go in general in relation to their top locations.</p

Cumulative distribution function (CDF) of the number of Foursquare users' friends who have previously checked in at the check-in venue in the dataset.

<p>The figure shows the functions for ‘social’ check-ins (part of a colocation between friends) and for all check-ins. Social check-ins are more likely to take place at venues where at least one of the user's friends has been than check-ins in general.</p

Cumulative distribution function (CDF) of the number of previous calls made or received by a cellphone user at a location, for colocated groups of various sizes.

<p>Pairs are more likely to meet at new places, in agreement with the Foursquare data, but bigger groups than this tend to meet at familiar locations.</p

Cumulative distribution function (CDF) of the number of previous check-ins by a Foursquare user to the check-in venue.

<p>The figure shows the functions for ‘social’ check-ins (part of a colocation between friends) and for all check-ins. Social check-ins are more likely to take place at new venues than check-ins in general.</p

Cumulative distribution function (CDF) of the number of previous calls made or received by a cellphone user at a location.

<p>The figure shows the functions for group colocations and for all calls. Group colocations are less likely to take place at new places, contrary to what was seen for pairs in the Foursquare data.</p

Ratio of the proportion of ‘social’ check-ins (part of a colocation between friends) in each category to the proportion of all check-ins in that category, for each of the categories of venue defined by Foursquare.

<p>Red bars show categories where social check-ins are under-represented (ratio <0.75), yellow bars those where social check-ins are approximately in the same proportion as solo check-ins (ratio 0.75–1.25), and green bars show categories where social check-ins are over-represented (ratio >1.25). Social check-ins are particularly likely to take place at venues in the Arts and Nightlife categories, and particularly unlikely to take place at venues in the Residence, Shop, and Transport categories.</p