parse_date_time
parses an input vector into POSIXct date-time
object. It differs from strptime
in two respects. First,
it allows specification of the order in which the formats occur without the
need to include separators and "%" prefix. Such a formating argument is
refered 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 as
strptime
.
parse_date_time(x, orders, tz = "UTC", truncated = 0, quiet = FALSE,
locale = Sys.getlocale("LC_TIME"), select_formats = .select_formats,
exact = FALSE)parse_date_time2(x, orders, tz = "UTC", exact = FALSE, lt = FALSE)
fast_strptime(x, format, tz = "UTC", lt = TRUE)
a character or numeric vector of dates
a character vector of date-time formats. Each order string is
series of formatting characters as listed 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 implemented
formats.
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 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 dates like
2012-06-01 12:23
, 2012-06-01 12
and
2012-06-01
. NOTE: ymd
family of functions are based
on strptime
which currently fails to parse %y-%m
formats.
logical. When TRUE progress messages are not printed, and
"no formats found" error is surpresed and the function simply returns a
vector of NAs. This mirrors the behavior of base R functions
strptime
and as.POSIXct
. Default is FALSE.
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 formating tockens (%) are
selected and %Y counts as 2.5 tockens (so that it has a priority over
%y%m). Se examples.
logical. If TRUE
, orders
parameter is interpreted
as an exact strptime
format and no trainign or guessing are
performed.
logical. If TRUE returned object is of class POSIXlt, and POSIXct otherwise. For compatibility with base `strptime` function default is TRUE for `fast_strptime` and FALSE for `parse_date_time2`.
a character string of formats. It should include all the
separators and each format must be prefixed with
argument of strptime
.
a vector of POSIXct date-time objects
When several format-orders are specified parse_date_time
sorts the
supplied format-orders based on a training set and then applies them
recursively on the input vector.
parse_date_time
, and all derived functions, such as ymd_hms
,
ymd
etc, will drop into fast_strptime
instead of
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 "*". 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 need not specify a
and A
formats explicitly. Wday is
automatically handled if preproc_wday = TRUE
b
!Abbreviated month name in the current locale (also matches full name). C parser understands English months only.
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 parsed month
if m
format is present.
m
!*Month as decimal number (01--12 or 1--12). For
parse_date_time
. As lubridate extension, 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. Normally used in conjunction
with I
and not with H
. But lubridate
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
strptime doesn't fully support ISO8601 this format is implemented as an
union of 4 orders: Ou (Z), Oz (-0800), OO (-08:00) and Oo (-08). You can use
these four orders as any other but it is rarely
necessary. parse_date_time2
and fast_strptime
support all of
the timezone 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.
# NOT RUN { ## ** orders are much easier to write ** x <- c("09-01-01", "09-01-02", "09-01-03") parse_date_time(x, "ymd") parse_date_time(x, "y m d") parse_date_time(x, "%y%m%d") # "2009-01-01 UTC" "2009-01-02 UTC" "2009-01-03 UTC" ## ** heterogenuous date-times ** x <- c("09-01-01", "090102", "09-01 03", "09-01-03 12:02") parse_date_time(x, c("ymd", "ymd HM")) ## ** different ymd orders ** x <- c("2009-01-01", "02022010", "02-02-2010") parse_date_time(x, c("dmY", "ymd")) ## "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) ## ** 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) 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) ## ** quarters and partial dates ** parse_date_time(c("2016.2", "2016-04"), orders = "Yq") parse_date_time(c("2016", "2016-04"), orders = c("Y", "Ym")) ## ** fast parsing ** # } # NOT RUN { 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) # } # NOT RUN { ## ** how to use `select_formats` argument ** ## By default %Y has precedence: parse_date_time(c("27-09-13", "27-09-2013"), "dmy") ## to give priority to %y format, define your own select_format function: my_select <- function(trained){ 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) ## ** invalid times with "fast" parcing ** parse_date_time("2010-03-14 02:05:06", "YmdHMS", tz = "America/New_York") parse_date_time2("2010-03-14 02:05:06", "YmdHMS", tz = "America/New_York") parse_date_time2("2010-03-14 02:05:06", "YmdHMS", tz = "America/New_York", lt = TRUE) # }