Title: | Fast Utility Function for Time Parsing and Conversion |
---|---|
Description: | Fast functions for timestamp manipulation that avoid system calls and take shortcuts to facilitate operations on very large data. |
Authors: | Simon Urbanek <[email protected]> |
Maintainer: | Simon Urbanek <[email protected]> |
License: | GPL-2 |
Version: | 1.1-0 |
Built: | 2024-08-24 02:58:17 UTC |
Source: | https://github.com/s-u/fasttime |
as.POSIXct.character
for GMT fixed format.
fastPOSIXct
converts timestamps in textual (string) form into
POSIXct
objects. It interprets sequences of digits
separated by non-digits as a timestamp in GMT. The order of
interpretation is fixed: year, month, day, hour, minute, second.
Note that only true (positive) POSIX dates (since 1970-01-01 00:00:00)
are supported and fastPOSIXct
accepts dates up to year 2199.
It is extremely fast (compared to as.POSIXct
by several orders
of magnitude (on some platforms 1000x faster) since it uses pure text
parsing and no system calls.
fastDate
is a faster shorthand for
as.Date(fastPOSIXct(x, "GMT", 3L, fixed))
.
fastPOSIXct(x, tz = NULL, required.components = 3L, fixed = NA) fastDate(x, fixed = NA)
fastPOSIXct(x, tz = NULL, required.components = 3L, fixed = NA) fastDate(x, fixed = NA)
x |
string vector to interpret as timestamps |
tz |
timezone for the resulting |
required.components |
minimum number of timestamp components that
are required. For example 3 means only the date is required, 6 means
all components (up to the seconds) are required. If the requirement
is not met, the result for that entry will be |
fixed |
|
By default the parsing is done by extracting digits separated by
non-digits. Each such group of digits is then interpreted in the
order year, month, day, hour, minute and seconds. The separators can
be arbitrary and of any length. Years less than 100 are assumed to be
2000..2099. For example, "2022-01-05 09:15"
has five groups
(from year to minute). The same timestamp would also be parsed from
"22/1/1, time 9:15"
or the ISO standard GMT form
"2022-01-01T09:15:00Z"
.
If the format uses no separators then fixed
can be set to the
length of the year component (in digits) – months through
minutes are assumed to have at most two digits each. For example, the
following call will have the same timestamp result as above:
fastPOSIXct("2201010915", fixed=2)
. Note that separators are
still allowed in the fixed parsing and will terminate the preceding
group so "220101 9:15"
would yield the same result.
Numeric vector of the class POSIXct
(fastPOSIXct
) or
Date
(fastDate
).
Simon Urbanek
## let us generate a bunch of random timestamps until today ts <- as.character(.POSIXct(runif(1e4) * unclass(Sys.time()), "GMT")) ## convert them using as.POSIXct system.time(a <- as.POSIXct(ts, "GMT")) ## same using the fast method system.time(b <- fastPOSIXct(ts, "GMT")) identical(a, b) ## same for dates day <- substr(ts, 1, 10) system.time(da <- as.Date(day)) system.time(db <- fastDate(day)) identical(da, db) ## some parsing examples fastPOSIXct("2022-01-05 09:15", "GMT") fastPOSIXct("22/1/1, the time is 9:15", "GMT") fastPOSIXct("2022-01-01T09:15:00Z", "GMT") fastPOSIXct("2201010915", "GMT", fixed=2) ## the same converted to your local time zone fastPOSIXct("2022-01-05 09:15") ## or ET fastPOSIXct("2022-01-05 09:15", "US/Eastern")
## let us generate a bunch of random timestamps until today ts <- as.character(.POSIXct(runif(1e4) * unclass(Sys.time()), "GMT")) ## convert them using as.POSIXct system.time(a <- as.POSIXct(ts, "GMT")) ## same using the fast method system.time(b <- fastPOSIXct(ts, "GMT")) identical(a, b) ## same for dates day <- substr(ts, 1, 10) system.time(da <- as.Date(day)) system.time(db <- fastDate(day)) identical(da, db) ## some parsing examples fastPOSIXct("2022-01-05 09:15", "GMT") fastPOSIXct("22/1/1, the time is 9:15", "GMT") fastPOSIXct("2022-01-01T09:15:00Z", "GMT") fastPOSIXct("2201010915", "GMT", fixed=2) ## the same converted to your local time zone fastPOSIXct("2022-01-05 09:15") ## or ET fastPOSIXct("2022-01-05 09:15", "US/Eastern")