time_round {timechange} | R Documentation |
timechange provides rounding to the nearest unit or multiple of a unit. Units can be specified flexibly as strings; all common abbreviations are supported - secs, min, mins, 2 minutes, 3 years, 2s, 1d etc.
time_round()
takes a date-time object and rounds it to the
nearest value of the specified time unit. For rounding date-times which is
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" per IEC
60559.
time_floor
takes a date-time object and rounds it down to the
nearest boundary of the specified time unit.
time_ceiling()
takes a date-time object and rounds it up to the
nearest boundary of the specified time unit.
time_round(time, unit = "second", week_start = getOption("week_start", 1)) time_floor(time, unit = "seconds", week_start = getOption("week_start", 1)) time_ceiling(time, unit = "seconds", change_on_boundary = inherits(time, "Date"), week_start = getOption("week_start", 1))
time |
a date-time vector ( |
unit |
a character string specifying a time unit or a multiple of a
unit. Valid base periods for civil time rounding are |
week_start |
when unit is |
change_on_boundary |
If NULL (the default) don't change instants on the
boundary ( |
An object of the same class as the input object. When input is a
Date
object and unit is smaller than day
a POSIXct
object is
returned.
Rounding in civil time is done on actual clock time (ymdHMS) and is affected by civil time irregularities like DST. One important characteristic of civil time rounding is that floor (ceiling) does not produce civil times that are bigger (smaller) than the rounded civil time.
Absolute time rounding (with aseconds
) is done on the absolute time (number
of seconds since origin), Thus, rounding of aseconds
allows for fractional
seconds and multi-units larger than 60. See examples of rounding around DST
transition where rounding in civil time does not give same result as rounding
with the corresponding X aseconds
.
Please note that absolute rounding to fractions smaller than 1ms will result to large precision errors due to the floating point representation of the POSIXct objects.
Date
objectsBy 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 up a day to its lower boundary.
The behavior on the boundary can be changed by setting
change_on_boundary
to a non-NULL
value.
If 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 <- as.POSIXct("2009-08-03 12:01:59.23") time_round(x, ".5 asec") time_round(x, "sec") time_round(x, "second") time_round(x, "asecond") time_round(x, "minute") time_round(x, "5 mins") time_round(x, "5M") # "M" for minute "m" for month time_round(x, "hour") time_round(x, "2 hours") time_round(x, "2H") time_round(x, "day") time_round(x, "week") time_round(x, "month") time_round(x, "bimonth") time_round(x, "quarter") == time_round(x, "3 months") time_round(x, "halfyear") time_round(x, "year") x <- as.POSIXct("2009-08-03 12:01:59.23") time_floor(x, ".1 asec") time_floor(x, "second") time_floor(x, "minute") time_floor(x, "M") time_floor(x, "hour") time_floor(x, "day") time_floor(x, "week") time_floor(x, "m") time_floor(x, "month") time_floor(x, "bimonth") time_floor(x, "quarter") time_floor(x, "season") time_floor(x, "halfyear") time_floor(x, "year") x <- as.POSIXct("2009-08-03 12:01:59.23") time_ceiling(x, ".1 asec") time_ceiling(x, "second") time_ceiling(x, "minute") time_ceiling(x, "5 mins") time_ceiling(x, "hour") time_ceiling(x, "day") time_ceiling(x, "week") time_ceiling(x, "month") time_ceiling(x, "bimonth") == time_ceiling(x, "2 months") time_ceiling(x, "quarter") time_ceiling(x, "season") time_ceiling(x, "halfyear") time_ceiling(x, "year") ## behavior on the boundary x <- as.Date("2000-01-01") time_ceiling(x, "month") time_ceiling(x, "month", change_on_boundary = FALSE) ## As of R 3.4.2 POSIXct printing of fractional numbers is wrong as.POSIXct("2009-08-03 12:01:59.3", tz = "UTC") ## -> "2009-08-03 12:01:59.2 UTC" time_ceiling(x, ".1 asec") ## -> "2009-08-03 12:01:59.2 UTC" ## Civil Time vs Absolute Time Rounding # "2014-11-02 01:59:59.5 EDT" before 1h backroll at 2AM x <- .POSIXct(1414907999.5, tz = "America/New_York") x time_ceiling(x, "hour") # "2014-11-02 02:00:00 EST" time_ceiling(x, "minute") time_ceiling(x, "sec") difftime(time_ceiling(x, "s"), x) time_ceiling(x, "1a") # "2014-11-02 01:00:00 EST" difftime(time_ceiling(x, "a"), x) # "2014-11-02 01:00:00.5 EST" after 1h backroll at 2AM x <- .POSIXct(1414908000.5, tz = "America/New_York") x time_floor(x, "hour") # "2014-11-02 01:00:00 EST" difftime(time_floor(x, "hour"), x) time_floor(x, "3600a") # "2014-11-02 01:00:00 EST" - 25m difftime(time_floor(x, "a"), x)