# login and logout vectors
login<-c(as.POSIXct("2016-04-23 10:18:04 UTC"),
         as.POSIXct("2016-04-28 09:14:18 UTC"),
         as.POSIXct("2016-04-28 12:21:51 UTC"),
         as.POSIXct("2016-04-28 12:37:24 UTC"),
         as.POSIXct("2016-04-30 21:37:55 UTC"))

logout<-c(as.POSIXct("2016-04-23 10:56:29 UTC"),
          as.POSIXct("2016-04-28 09:14:52 UTC"),
          as.POSIXct("2016-04-28 12:35:48 UTC"),
          as.POSIXct("2016-04-28 13:17:22 UTC"),
          as.POSIXct("2016-04-30 22:08:47 UTC"))
