parse_date_time()
parses an input vector into POSIXct date-time
object. It differs from base::strptime()
in two respects. First,
it allows specification of the order in which the formats occur without the
need to include separators and the %
prefix. Such a formatting argument is
referred to as "order". Second, it allows the user to specify several
format-orders to handle heterogeneous date-time character
representations.
parse_date_time2()
is a fast C parser of numeric orders.
fast_strptime()
is a fast C parser of numeric formats only
that accepts explicit format arguments, just like base::strptime()
.
parse_date_time(
x,
orders,
tz = "UTC",
truncated = 0,
quiet = FALSE,
locale = Sys.getlocale("LC_TIME"),
select_formats = .select_formats,
exact = FALSE,
train = TRUE,
drop = FALSE
)
parse_date_time2(
x,
orders,
tz = "UTC",
exact = FALSE,
lt = FALSE,
cutoff_2000 = 68L
)
fast_strptime(x, format, tz = "UTC", lt = TRUE, cutoff_2000 = 68L)
a character or numeric vector of dates
a character vector of date-time formats. Each order string is
a series of formatting characters as listed in base::strptime()
but
might not include the "%"
prefix. For example, "ymd" will match all the
possible dates in year, month, day order. Formatting orders might include
arbitrary separators. These are discarded. See details for the implemented
formats. If multiple order strings are supplied, they are applied in turn
for parse_date_time2()
and fast_strptime()
. For parse_date_time()
the order of applied formats is determined by select_formats
parameter.
a character string that specifies the time zone with which to parse the dates
integer, number of formats that can be missing. The most
common type of irregularity in date-time data is the truncation due to
rounding or unavailability of the time stamp. If the truncated
parameter
is non-zero parse_date_time()
also checks for truncated formats. For
example, if the format order is "ymdHMS" and truncated = 3
,
parse_date_time()
will correctly parse incomplete date-times like
2012-06-01 12:23
, 2012-06-01 12
and 2012-06-01
. NOTE: The
ymd()
family of functions is based on base::strptime()
which currently
fails to parse %Y-%m
formats.
logical. If TRUE
, progress messages are not printed, and No formats found
error is suppressed and the function simply returns a
vector of NAs. This mirrors the behavior of base R functions
base::strptime()
and base::as.POSIXct()
.
locale to be used, see locales. On Linux systems you
can use system("locale -a")
to list all the installed locales.
A function to select actual formats for parsing from a
set of formats which matched a training subset of x
. It receives a named
integer vector and returns a character vector of selected formats. Names
of the input vector are formats (not orders) that matched the training
set. Numeric values are the number of dates (in the training set) that
matched the corresponding format. You should use this argument if the
default selection method fails to select the formats in the right
order. By default the formats with most formatting tokens (%
) are
selected and %Y
counts as 2.5 tokens (so that it has a priority over
%y%m
). See examples.
logical. If TRUE
, the orders
parameter is interpreted as an
exact base::strptime()
format and no training or guessing are performed
(i.e. train
, drop
parameters are ignored).
logical, default TRUE
. Whether to train formats on a subset
of the input vector. The result of this is that supplied orders are sorted
according to performance on this training set, which commonly results in
increased performance. Please note that even when train = FALSE
(and
exact = FALSE
) guessing of the actual formats is still performed on a
pseudo-random subset of the original input vector. This might result in
All formats failed to parse
error. See notes below.
logical, default FALSE
. Whether to drop formats that didn't
match on the training set. If FALSE
, unmatched on the training set
formats are tried as a last resort at the end of the parsing
queue. Applies only when train = TRUE
. Setting this parameter to TRUE
might slightly speed up parsing in situations involving many
formats. Prior to v1.7.0 this parameter was implicitly TRUE
, which
resulted in occasional surprising behavior when rare patterns where not
present in the training set.
logical. If TRUE
, returned object is of class POSIXlt, and POSIXct
otherwise. For compatibility with base::strptime()
the default is TRUE
for fast_strptime()
and FALSE
for parse_date_time2()
.
integer. For y
format, two-digit numbers smaller or equal
to cutoff_2000
are parsed as though starting with 20
, otherwise parsed
as though starting with 19
. Available only for functions relying on
lubridate
s internal parser.
a vector of formats. If multiple formats supplied they are
applied in turn till success. The formats should include all the
separators and each format letter must be prefixed with %, just as in the
format argument of base::strptime()
.
a vector of POSIXct date-time objects
When several format-orders are specified, parse_date_time()
selects
(guesses) format-orders based on a training subset of the input
strings. After guessing the formats are ordered according to the performance
on the training set and applied recursively on the entire input vector. You
can disable training with train = FALSE
.
parse_date_time()
, and all derived functions, such as ymd_hms()
,
ymd()
, etc., will drop into fast_strptime()
instead of
base::strptime()
whenever the guessed from the input data formats are all
numeric.
The list below contains formats recognized by lubridate. For numeric
formats leading 0s are optional. As compared to base::strptime()
, some of
the formats are new or have been extended for efficiency reasons. These
formats are marked with "(*)" below. Fast parsers parse_date_time2()
and
fast_strptime()
accept only formats marked with "(!)".
a
Abbreviated weekday name in the current locale. (Also matches full name)
A
Full weekday name in the current locale. (Also matches abbreviated name).
You don't need to specify a
and A
formats explicitly. Wday is
automatically handled if preproc_wday = TRUE
b
(!)Abbreviated or full month name in the current locale. The C parser currently understands only English month names.
B
(!)Same as b.
d
(!)Day of the month as decimal number (01--31 or 0--31)
H
(!)Hours as decimal number (00--24 or 0--24).
I
(!)Hours as decimal number (01--12 or 1--12).
j
Day of year as decimal number (001--366 or 1--366).
q
(!*)Quarter (1--4). The quarter month is added to the parsed
month if m
element is present.
m
(!*)Month as decimal number (01--12 or 1--12). For
parse_date_time
also matches abbreviated and full months names as b
and B
formats. C parser understands only English month names.
M
(!)Minute as decimal number (00--59 or 0--59).
p
(!)AM/PM indicator in the locale. Commonly used in conjunction
with I
and not with H
. But lubridate's C parser accepts H
format as long as hour is not greater than 12. C parser understands only
English locale AM/PM indicator.
S
(!)Second as decimal number (00--61 or 0--61), allowing for up to two leap-seconds (but POSIX-compliant implementations will ignore leap seconds).
OS
Fractional second.
U
Week of the year as decimal number (00--53 or 0--53) using Sunday as the first day 1 of the week (and typically with the first Sunday of the year as day 1 of week 1). The US convention.
w
Weekday as decimal number (0--6, Sunday is 0).
W
Week of the year as decimal number (00--53 or 0--53) using Monday as the first day of week (and typically with the first Monday of the year as day 1 of week 1). The UK convention.
y
(!*)Year without century (00--99 or 0--99). In
parse_date_time()
also matches year with century (Y format).
Y
(!)Year with century.
z
(!*)ISO8601 signed offset in hours and minutes from UTC. For
example -0800
, -08:00
or -08
, all represent 8 hours behind UTC. This
format also matches the Z (Zulu) UTC indicator. Because base::strptime()
doesn't fully support ISO8601 this format is implemented as an union of 4
formats: Ou (Z), Oz (-0800), OO (-08:00) and Oo (-08). You can use these
formats as any other but it is rarely necessary. parse_date_time2()
and
fast_strptime()
support all of these formats.
Om
(!*)Matches numeric month and English alphabetic months (Both, long and abbreviated forms).
Op
(!*)Matches AM/PM English indicator.
r
(*)Matches Ip
and H
orders.
R
(*)Matches HM
andIMp
orders.
T
(*)Matches IMSp
, HMS
, and HMOS
orders.
parse_date_time()
(and the derivatives ymd()
, ymd_hms()
, etc.)
relies on a sparse guesser that takes at most 501 elements from the
supplied character vector in order to identify appropriate formats from
the supplied orders. If you get the error All formats failed to parse
and you are confident that your vector contains valid dates, you should
either set exact
argument to TRUE
or use functions that don't perform
format guessing (fast_strptime()
, parse_date_time2()
or
base::strptime()
).
For performance reasons, when timezone is not UTC,
parse_date_time2()
and fast_strptime()
perform no validity checks for
daylight savings time. Thus, if your input string contains an invalid date
time which falls into DST gap and lt = TRUE
you will get an POSIXlt
object with a non-existent time. If lt = FALSE
your time instant will be
adjusted to a valid time by adding an hour. See examples. If you want to
get NA for invalid date-times use fit_to_timeline()
explicitly.
## ** orders are much easier to write **
x <- c("09-01-01", "09-01-02", "09-01-03")
parse_date_time(x, "ymd")
#> [1] "2009-01-01 UTC" "2009-01-02 UTC" "2009-01-03 UTC"
parse_date_time(x, "y m d")
#> [1] "2009-01-01 UTC" "2009-01-02 UTC" "2009-01-03 UTC"
parse_date_time(x, "%y%m%d")
#> [1] "2009-01-01 UTC" "2009-01-02 UTC" "2009-01-03 UTC"
# "2009-01-01 UTC" "2009-01-02 UTC" "2009-01-03 UTC"
## ** heterogeneous date-times **
x <- c("09-01-01", "090102", "09-01 03", "09-01-03 12:02")
parse_date_time(x, c("ymd", "ymd HM"))
#> [1] "2009-01-01 00:00:00 UTC" "2009-01-02 00:00:00 UTC"
#> [3] "2009-01-03 00:00:00 UTC" "2009-01-03 12:02:00 UTC"
## ** different ymd orders **
x <- c("2009-01-01", "02022010", "02-02-2010")
parse_date_time(x, c("dmY", "ymd"))
#> [1] "2009-01-01 UTC" "2010-02-02 UTC" "2010-02-02 UTC"
## "2009-01-01 UTC" "2010-02-02 UTC" "2010-02-02 UTC"
## ** truncated time-dates **
x <- c("2011-12-31 12:59:59", "2010-01-01 12:11", "2010-01-01 12", "2010-01-01")
parse_date_time(x, "Ymd HMS", truncated = 3)
#> [1] "2011-12-31 12:59:59 UTC" "2010-01-01 12:11:00 UTC"
#> [3] "2010-01-01 12:00:00 UTC" "2010-01-01 00:00:00 UTC"
## ** specifying exact formats and avoiding training and guessing **
parse_date_time(x, c("%m-%d-%y", "%m%d%y", "%m-%d-%y %H:%M"), exact = TRUE)
#> Warning: 4 failed to parse.
#> [1] NA NA NA NA
parse_date_time(c('12/17/1996 04:00:00','4/18/1950 0130'),
c('%m/%d/%Y %I:%M:%S','%m/%d/%Y %H%M'), exact = TRUE)
#> [1] "1996-12-17 04:00:00 UTC" "1950-04-18 01:30:00 UTC"
## ** quarters and partial dates **
parse_date_time(c("2016.2", "2016-04"), orders = "Yq")
#> [1] "2016-04-01 UTC" "2016-10-01 UTC"
parse_date_time(c("2016", "2016-04"), orders = c("Y", "Ym"))
#> [1] "2016-01-01 UTC" "2016-04-01 UTC"
## ** fast parsing **
if (FALSE) {
options(digits.secs = 3)
## random times between 1400 and 3000
tt <- as.character(.POSIXct(runif(1000, -17987443200, 32503680000)))
tt <- rep.int(tt, 1000)
system.time(out <- as.POSIXct(tt, tz = "UTC"))
system.time(out1 <- ymd_hms(tt)) # constant overhead on long vectors
system.time(out2 <- parse_date_time2(tt, "YmdHMOS"))
system.time(out3 <- fast_strptime(tt, "%Y-%m-%d %H:%M:%OS"))
all.equal(out, out1)
all.equal(out, out2)
all.equal(out, out3)
}
## ** how to use `select_formats` argument **
## By default %Y has precedence:
parse_date_time(c("27-09-13", "27-09-2013"), "dmy")
#> [1] "2013-09-27 UTC" "2013-09-27 UTC"
## to give priority to %y format, define your own select_format function:
my_select <- function(trained, drop=FALSE, ...){
n_fmts <- nchar(gsub("[^%]", "", names(trained))) + grepl("%y", names(trained))*1.5
names(trained[ which.max(n_fmts) ])
}
parse_date_time(c("27-09-13", "27-09-2013"), "dmy", select_formats = my_select)
#> [1] "2013-09-27 UTC" "2013-09-27 UTC"
## ** invalid times with "fast" parsing **
parse_date_time("2010-03-14 02:05:06", "YmdHMS", tz = "America/New_York")
#> Warning: 1 failed to parse.
#> [1] NA
parse_date_time2("2010-03-14 02:05:06", "YmdHMS", tz = "America/New_York")
#> [1] "2010-03-14 03:05:06 EDT"
parse_date_time2("2010-03-14 02:05:06", "YmdHMS", tz = "America/New_York", lt = TRUE)
#> [1] "2010-03-14 02:05:06 America/New_York"