I have the following input: session id, login time, logout time. I'm trying to get a graph of concurrent active users within the login/logout time range. For example if i have the following dataset: sid, login time, logout 1, 2014-05-26 11:00, 2014-05-26 15:00 2, 2014-05-26 12:00, 2014-05-26 13:00 3, 2014-05-26 13:00, 2014-05-26 14:00 I would like to get a graph which span on each hour with the following results: 11:00-12:00 1 concurrent users 12:00-13:00 2 concurrent users 14:00-15:00 2 concurrent users ... View more