regex - How to most efficiently convert a character string of "01 Jan 2014" to POSIXct i.e. "2014-01-01" yyyy-mm-dd -


i have partial answer problem here, understand far explained: how efficiently restructure character string fasttime in data.table

however, task has been extended, , needs deal variation of orginal formatting.

i have large dataset, column of dates of character class in form of:

01 jan 2014

or:

dd mmm yyyy

which want restructure feed fastposixct accepts character input in posixct order:

yyyy-mm-dd

the above linked question notes efficient approach use regex , supply output fast.time. here need extend include method understand monthly abbreviations, convert numeric, rearrange? how this? know there month.abb built in constant. should using this, or there smarter way?

what using lubridate:

x <- "01 jan 2014" x [1] "01 jan 2014" library(lubridate) dmy(x) [1] "2014-01-01 utc"

of course lubridate functions accept tz argument too. see complete list of acceptable arguments see olsonnames()

benchmark

i decided update answer empirical data using micro benchmark package , lubridate option use fasstime.

library(micro benchmark) microbenchmark(dmy(x), times = 10000) unit: milliseconds    expr      min      lq     mean   median      uq     max neval  dmy(x) 1.992639 2.02567 2.142212 2.041514 2.07153 39.1384 10000  options(lubridate.fasttime = t)  microbenchmark(dmy(x), times = 10000) unit: milliseconds    expr      min      lq     mean   median       uq      max neval  dmy(x) 1.993326 2.02488 2.136748 2.039467 2.065326 163.2008 10000

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