R: Anything to 'POSIXct' or 'Date' Converter

anytime-package {anytime} | R Documentation

## Anything to 'POSIXct' or 'Date' Converter

### Description

Convert input in any one of character, integer, numeric, factor, or ordered type into 'POSIXct' (or 'Date') objects, using one of a number of predefined formats, and relying on Boost facilities for date and time parsing.

### Details

R excels at computing with dates, and times. Using typed representation for your data is highly recommended not only because of the functionality offered but also because of the added safety stemming from proper representation.

But there is a small nuisance cost in interactive work as well as in programming. How often have we told `as.POSIXct()` that the origin is (of course) the epoch. Do we really have to say it again? Similarly, when parsing dates that are somewhat in YYYYMMDD format, do we really need to bother converting from integer or numeric or character or factor or ordered with one of dozen separators and/or month forms: YYYY-MM-DD, YYYY/MM/DD, YYYYMMDD, YYYY-mon-DD and so on?

So there may have been a need for a general purpose converter returning a proper `POSIXct` (or `Date`) object no matter the input (provided it was somewhat parseable). `anytime()` tries to be that function.

The actual conversion is done by a combination of Boost lexical_cast to go from (almost) anything to string representation which is then parsed by Boost Date_Time. An alternate method using the corresponding R functions is also available as a fallback.

Conversion is done by looping over a fixed set of formats until a matching one is found, or returning an error if none is found. The current set of conversion formulae is accessible in the source code, and can now also be accessed in R via `getFormats()`. Formats can be added and removed via the `addFormats()` and `removeFormats{}` functions.

Details on the Boost date format symbols are provided by the Boost date_time documentation and similar (but not identical) to what `strftime` uses.

### Author(s)

Dirk Eddelbuettel

### References

Boost date_time: https://www.boost.org/doc/libs/1_70_0/doc/html/date_time.html

Formats used: https://github.com/eddelbuettel/anytime/blob/master/src/anytime.cpp#L43-L106

Boost format documentation: https://www.boost.org/doc/libs/1_61_0/doc/html/date_time/date_time_io.html#date_time.format_flags

### Examples

      Sys.setenv(TZ=anytime:::getTZ())      ## helper function to try to get TZ
      options(digits.secs=6)                ## for fractional seconds below

      library(anytime)                      ## load package, caches TZ information

      ## integer
      anydate(20160101L + 0:2)

      ## numeric
      anydate(20160101 + 0:2)

      ## factor
      anydate(as.factor(20160101 + 0:2))

      ## ordered
      anydate(as.ordered(20160101 + 0:2))

      ## Dates: Character
      anydate(as.character(20160101 + 0:2))

      ## Dates: alternate formats
      anydate(c("20160101", "2016/01/02", "2016-01-03"))

      ## Datetime: ISO with/without fractional seconds
      anytime(c("2016-01-01 10:11:12", "2016-01-01 10:11:12.345678"))

      ## Datetime: ISO alternate (?) with 'T' separator
      anytime(c("20160101T101112", "20160101T101112.345678"))

      ## Short month '%b' (and full month is supported too)
      anytime(c("2016-Sep-01 10:11:12", "Sep/01/2016 10:11:12", "Sep-01-2016 10:11:12"))

      ## Datetime: Mixed format (cf https://stackoverflow.com/questions/39259184)
      anytime(c("Thu Sep 01 10:11:12 2016", "Thu Sep 01 10:11:12.345678 2016"))

[Package anytime version 0.3.9 Index]