> dput(head(mydata))
structure(list(day = 1:6, on.mains = c(0L, 0L, 0L, 0L, 0L, 0L
), on.tank = 0:5, date2 = 18890101:18890106, year = c(1889, 1889,
1889, 1889, 1889, 1889), On.which = c("on.tank", "on.tank", "on.tank",
"on.tank", "on.tank", "on.tank"), id2 = c(1L, 1L, 1L, 1L, 1L,
1L)), row.names = c(NA, 6L), class = "data.frame")

> dput(tail(mydata))
structure(list(day = 47220:47225, on.mains = c(0L, 0L, 0L, 0L,
0L, 0L), on.tank = 48:53, date2 = 20180414:20180419, year = c(2018,
2018, 2018, 2018, 2018, 2018), On.which = c("on.tank", "on.tank",
"on.tank", "on.tank", "on.tank", "on.tank"), id2 = c(130L, 130L,
130L, 130L, 130L, 130L)), row.names = 47220:47225, class = "data.frame")
>