given two intervals, figure out the intersection between the
first and the second
NOTE that the intervals are treated as half-open (start,finish]
so that an event that happens exactly at time b is counted in
(a,b] but not in (b, c]
Arguments
- a
the first window; here, we use all three components
(start, finish, event)
- b
the second window; here, we only use the start and finish
time, and ignore any events
Value
a window containing the exposure and events from a that takes place
during the time given by b; also, if a has an event and it takes
place during b, it is included
Details
TODO - should write a more detailed description