dput:
tides <- structure(list(Date = structure(c(15L, 16L, 1L, 2L, 3L, 4L, 5L,
5L, 6L, 6L, 7L, 7L, 8L, 8L, 9L, 10L, 11L, 12L, 13L, 14L), .Label = c("11/10/2017",
"11/11/2017", "11/12/2017", "11/13/2017", "11/14/2017", "11/15/2017",
"11/16/2017", "11/17/2017", "11/18/2017", "11/19/2017", "11/20/2017",
"11/21/2017", "11/22/2017", "11/23/2017", "11/8/2017", "11/9/2017"
), class = "factor"), Site = structure(c(1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "LCOR_1", class = "factor"),
Camera = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "HC500", class = "factor"),
Start.Low.Tide = structure(c(3L, 13L, 14L, 1L, 2L, 4L, 10L,
5L, 9L, 6L, 9L, 7L, 9L, 8L, 9L, 10L, 9L, 11L, 11L, 12L), .Label = c("10:00",
"12:05", "13:20", "13:40", "14:45", "15:50", "16:40", "17:55",
"7:30", "7:35", "7:40", "8:00", "8:40", "9:20"), class = "factor"),
End.Low.Tide = structure(c(10L, 11L, 12L, 14L, 12L, 14L,
15L, 14L, 2L, 13L, 1L, 13L, 4L, 13L, 3L, 5L, 8L, 6L, 7L,
9L), .Label = c("10:25", "10:30:00", "10:45", "10:55", "12:20",
"12:50", "13:25", "13:40", "14:35", "15:00:00", "15:45:00",
"18:30:00", "18:55", "18:55:00", "9:10:00"), class = "factor"),
Notes = structure(c(1L, 1L, 1L, 3L, 1L, 3L, 2L, 3L, 2L, 3L,
2L, 3L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("", "reef showing on the first frame of the day",
"reef showing on the last frame of the day"), class = "factor"),
Start.Date.Time = structure(c(1510165200, 1510234800, 1510323600,
1510412400, 1510506300, 1510598400, 1510662900, 1510688700,
1510749000, 1510779000, 1510835400, 1510868400, 1510921800,
1510959300, 1511008200, 1511094900, 1511181000, 1511268000,
1511354400, 1511442000), class = c("POSIXct", "POSIXt"), tzone = "EST"),
End.Date.Time = structure(c(NA, NA, NA, NA, NA, NA, NA, NA,
NA, 1510790100, 1510845900, 1510876500, 1510934100, 1510962900,
1511019900, 1511112000, 1511203200, 1511286600, 1511375100,
1511465700), class = c("POSIXct", "POSIXt"), tzone = "EST")), .Names = c("Date",
"Site", "Camera", "Start.Low.Tide", "End.Low.Tide", "Notes",
"Start.Date.Time", "End.Date.Time"), row.names = c(NA, 20L), class = "data.frame")
Неправильная переменная для интервала.Это должно быть: tides$interval <- interval(tides$Start.Date.Time, tides$End.Date.Time)
, так как это версия lubridate, которую вы рассчитали.