Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Illustration of how spatio-temporal co-occurrences are counted, for some sample time-stamped observations of individuals A and B. The world is divided into discrete cells of size s × s, and we count the number of cells k in which the two individuals have been observed within a time threshold of t days—in this case, k = 3 when t is 2.
