in reply to User tracking

Usually when analyzing log files you assume that each unique combination of user agent and IP is one user. You can analyze your log files on a day by day basis and simply subtract the timestamp of the first visit from that of the last visit, and get some measure for the time somebody stays if he loads at least two different pages.

That will give you some kind of flawed measure, but it's enough to give you a rough idea.

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Re^2: User tracking
by ig (Vicar) on May 18, 2009 at 10:58 UTC

    I always remember the day one of our major customers came to us, furiously demanding to know what we had done to block all their users. Their number of "visits" had dropped by about 80% and they were sure we had done something to prevent their users accessing the site. They also wanted us to track down one rogue user that now accounted for almost all the traffic to their site. That user, it turned out, had the IP address of our new proxy server. Flawed is a key concept in log analysis.

Re^2: User tracking
by CountZero (Bishop) on May 18, 2009 at 09:03 UTC
    That will give you some kind of flawed measure,
    The emphasis of course being on flawed. :-)

    CountZero

    A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James