Round, floor and ceiling methods for date-time objects
round_date() takes a date-time object and time unit, and rounds it to the nearest value
of the specified time unit. For rounding date-times which are exactly halfway
between two consecutive units, the convention is to round up. Note that this
is in line with the behavior of R's base::round.POSIXt() function
but does not follow the convention of the base base::round() function
which "rounds to the even digit", as per IEC 60559.
Rounding to the nearest unit or multiple of a unit is supported. All meaningful specifications in the English language are supported - secs, min, mins, 2 minutes, 3 years etc.
Rounding to fractional seconds is also supported. Please note that rounding to fractions smaller than 1 second can lead to large precision errors due to the floating point representation of the POSIXct objects. See examples.
floor_date() takes a date-time object and rounds it down to the nearest
boundary of the specified time unit.
ceiling_date() takes a date-time object and rounds it up to the nearest
boundary of the specified time unit.
round_date(
x,
unit = "second",
week_start = getOption("lubridate.week.start", 7)
)
floor_date(
x,
unit = "seconds",
week_start = getOption("lubridate.week.start", 7)
)
ceiling_date(
x,
unit = "seconds",
change_on_boundary = NULL,
week_start = getOption("lubridate.week.start", 7)
)x |
a vector of date-time objects |
unit |
a character string specifying a time unit or a multiple of a unit
to be rounded to. Valid base units are |
week_start |
when unit is |
change_on_boundary |
if this is |
In lubridate, functions that round date-time objects try to preserve the class of the input object whenever possible. This is done by first rounding to an instant, and then converting to the original class as per usual R conventions.
By default, rounding up Date objects follows 3 steps:
Convert to an instant representing lower bound of the Date:
2000-01-01 –> 2000-01-01 00:00:00
Round up to the next closest rounding unit boundary. For example,
if the rounding unit is month then next closest boundary of 2000-01-01
is 2000-02-01 00:00:00.
The motivation for this is that the "partial" 2000-01-01 is conceptually
an interval (2000-01-01 00:00:00 – 2000-01-02 00:00:00) and the day
hasn't started clocking yet at the exact boundary 00:00:00. Thus, it
seems wrong to round a day to its lower boundary.
Behavior on the boundary can be changed by setting
change_on_boundary to TRUE or FALSE.
If the rounding unit is smaller than a day, return the instant from step 2
(POSIXct), otherwise convert to and return a Date object.
## print fractional seconds
options(digits.secs=6)
x <- ymd_hms("2009-08-03 12:01:59.23")
round_date(x, ".5s")
round_date(x, "sec")
round_date(x, "second")
round_date(x, "minute")
round_date(x, "5 mins")
round_date(x, "hour")
round_date(x, "2 hours")
round_date(x, "day")
round_date(x, "week")
round_date(x, "month")
round_date(x, "bimonth")
round_date(x, "quarter") == round_date(x, "3 months")
round_date(x, "halfyear")
round_date(x, "year")
x <- ymd_hms("2009-08-03 12:01:59.23")
floor_date(x, ".1s")
floor_date(x, "second")
floor_date(x, "minute")
floor_date(x, "hour")
floor_date(x, "day")
floor_date(x, "week")
floor_date(x, "month")
floor_date(x, "bimonth")
floor_date(x, "quarter")
floor_date(x, "season")
floor_date(x, "halfyear")
floor_date(x, "year")
x <- ymd_hms("2009-08-03 12:01:59.23")
ceiling_date(x, ".1 sec") # imprecise representation at 0.1 sec !!!
ceiling_date(x, "second")
ceiling_date(x, "minute")
ceiling_date(x, "5 mins")
ceiling_date(x, "hour")
ceiling_date(x, "day")
ceiling_date(x, "week")
ceiling_date(x, "month")
ceiling_date(x, "bimonth") == ceiling_date(x, "2 months")
ceiling_date(x, "quarter")
ceiling_date(x, "season")
ceiling_date(x, "halfyear")
ceiling_date(x, "year")
## As of R 3.4.2 POSIXct printing of fractional numbers is wrong
as.POSIXct("2009-08-03 12:01:59.3") ## -> "2009-08-03 12:01:59.2 CEST"
ceiling_date(x, ".1 sec") ## -> "2009-08-03 12:01:59.2 CEST"
## behaviour of `change_on_boundary`
## As per default behaviour `NULL`, instants on the boundary remain the
## same but dates are rounded up
ceiling_date(ymd_hms("2000-01-01 00:00:00"), "month")
ceiling_date(ymd("2000-01-01"), "month")
## If `TRUE`, both instants and dates on the boundary are rounded up
ceiling_date(ymd_hms("2000-01-01 00:00:00"), "month", change_on_boundary = TRUE)
ceiling_date(ymd("2000-01-01"), "month")
## If `FALSE`, both instants and dates on the boundary remain the same
ceiling_date(ymd_hms("2000-01-01 00:00:00"), "month", change_on_boundary = FALSE)
ceiling_date(ymd("2000-01-01"), "month")
x <- ymd_hms("2000-01-01 00:00:00")
ceiling_date(x, "month")
ceiling_date(x, "month", change_on_boundary = TRUE)
## For Date objects first day of the month is not on the
## "boundary". change_on_boundary applies to instants only.
x <- ymd("2000-01-01")
ceiling_date(x, "month")
ceiling_date(x, "month", change_on_boundary = TRUE)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.