IDateTime
Integer based date class
Date and time classes with integer storage for fast sorting and grouping. Still experimental!
Usage
as.IDate(x, ...)
# S3 method for default
as.IDate(x, …)
# S3 method for Date
as.IDate(x, …)
# S3 method for IDate
as.Date(x, …)
# S3 method for IDate
as.POSIXct(x, tz = "UTC", time = 0, …)
# S3 method for IDate
as.chron(x, time = NULL, …)
# S3 method for IDate
round(x, digits = c("weeks", "months", "quarters","years"), …)as.ITime(x, ...)
# S3 method for default
as.ITime(x, …)
# S3 method for ITime
as.POSIXct(x, tz = "UTC", date = as.Date(Sys.time()), …)
# S3 method for ITime
as.chron(x, date = NULL, …)
# S3 method for ITime
as.character(x, …)
# S3 method for ITime
format(x, …)
IDateTime(x, ...)
# S3 method for default
IDateTime(x, ...)
second(x)
minute(x)
hour(x)
yday(x)
wday(x)
mday(x)
week(x)
isoweek(x)
month(x)
quarter(x)
year(x)
Arguments
- x
an object
- …
arguments to be passed to or from other methods. For
as.IDate.default
, arguments are passed toas.Date
. Foras.ITime.default
, arguments are passed toas.POSIXlt
.- tz
time zone (see
strptime
).- date
date object convertable with
as.IDate
.- time
time-of-day object convertable with
as.ITime
.- digits
really
units
; one of the units listed for rounding. May be abbreviated.
Details
IDate
is a date class derived from Date
. It has the same
internal representation as the Date
class, except the storage
mode is integer. IDate
is a relatively simple wrapper, and it
should work in almost all situations as a replacement for Date
.
Functions that use Date
objects generally work for
IDate
objects. This package provides specific methods for
IDate
objects for mean
, cut
, seq
, c
,
rep
, and split
to return an IDate
object.
ITime
is a time-of-day class stored as the integer number of
seconds in the day. as.ITime
does not allow days longer than 24
hours. Because ITime
is stored in seconds, you can add it to a
POSIXct
object, but you should not add it to a Date
object.
Conversions to and from Date
, POSIXct
, and chron
formats are provided.
ITime
does not account for time zones. When converting
ITime
and IDate
to POSIXct with as.POSIXct
, a time
zone may be specified.
In as.POSIXct
methods for ITime
and IDate
, the
second argument is required to be tz
based on the generic
template, but to make converting easier, the second arguement is
interpreted as a date instead of a time zone if it is of type
IDate
or ITime
. Therefore, you can use either of the
following: as.POSIXct(time, date)
or as.POSIXct(date,
time)
.
IDateTime
takes a date-time input and returns a data table with
columns date
and time
.
Using integer storage allows dates and/or times to be used as data table
keys. With positive integers with a range less than 100,000, grouping
and sorting is fast because radix sorting can be used (see
sort.list
).
Several convenience functions like hour
and quarter
are
provided to group or extract by hour, month, and other date-time
intervals. as.POSIXlt
is also useful. For example,
as.POSIXlt(x)$mon
is the integer month. The R base convenience
functions weekdays
, months
, and quarters
can also
be used, but these return character values, so they must be converted to
factors for use with data.table. isoweek
is ISO 8601-consistent.
The round
method for IDate's is useful for grouping and plotting. It can
round to weeks, months, quarters, and years.
Value
For as.IDate
, a class of IDate
and Date
with the
date stored as the number of days since some origin.
For as.ITime
, a class of ITime
stored as the number of seconds in the day.
For IDateTime
, a data table with columns idate
and
itime
in IDate
and ITime
format.
second
, minute
, hour
, yday
, wday
,
mday
, week
, month
, quarter
,
and year
return integer values
for second, minute, hour, day of year, day of week,
day of month, week, month, quarter, and year, respectively.
These values are all taken directly from the POSIXlt
representation of x
, with the notable difference that while yday
, wday
, and mon
are all 0-based, here they are 1-based.
References
G. Grothendieck and T. Petzoldt, ``Date and Time Classes in R,'' R News, vol. 4, no. 1, June 2004.
H. Wickham, http://gist.github.com/10238.
ISO 8601, http://www.iso.org/iso/home/standards/iso8601.htm
See Also
Examples
# NOT RUN {
# create IDate:
(d <- as.IDate("2001-01-01"))
# S4 coercion also works
identical(as.IDate("2001-01-01"), as("2001-01-01", "IDate"))
# create ITime:
(t <- as.ITime("10:45"))
# S4 coercion also works
identical(as.ITime("10:45"), as("10:45", "ITime"))
(t <- as.ITime("10:45:04"))
(t <- as.ITime("10:45:04", format = "%H:%M:%S"))
as.POSIXct("2001-01-01") + as.ITime("10:45")
datetime <- seq(as.POSIXct("2001-01-01"), as.POSIXct("2001-01-03"), by = "5 hour")
(af <- data.table(IDateTime(datetime), a = rep(1:2, 5), key = "a,idate,itime"))
af[, mean(a), by = "itime"]
af[, mean(a), by = list(hour = hour(itime))]
af[, mean(a), by = list(wday = factor(weekdays(idate)))]
af[, mean(a), by = list(wday = wday(idate))]
as.POSIXct(af$idate)
as.POSIXct(af$idate, time = af$itime)
as.POSIXct(af$idate, af$itime)
as.POSIXct(af$idate, time = af$itime, tz = "GMT")
as.POSIXct(af$itime, af$idate)
as.POSIXct(af$itime) # uses today's date
(seqdates <- seq(as.IDate("2001-01-01"), as.IDate("2001-08-03"), by = "3 weeks"))
round(seqdates, "months")
if (require(chron)) {
as.chron(as.IDate("2000-01-01"))
as.chron(as.ITime("10:45"))
as.chron(as.IDate("2000-01-01"), as.ITime("10:45"))
as.chron(as.ITime("10:45"), as.IDate("2000-01-01"))
as.ITime(chron(times = "11:01:01"))
IDateTime(chron("12/31/98","10:45:00"))
}
# }