R convert string date (e.g. “October 1, 2014”) to Date format

问题

how can I convert a vector of date string like c("October 1, 2014", "June 14, 2014") to a vector of R Date format?

I have a data.frame which one column is date string in the above format.

I would appreciate your help.

Thanks!

回答1:

Try:

v <- c("October 1, 2014", "June 14, 2014") 
as.Date(v, "%B %d,%Y")

Which gives:

#[1] "2014-10-01" "2014-06-14"

Or

strptime(v, "%B %d,%Y")

Which gives:

#[1] "2014-10-01 EDT" "2014-06-14 EDT"

---

Benchmark

largev <- rep(v, 10e5)

library(microbenchmark)
microbenchmark(
  as.Date = as.Date(largev, "%B %d,%Y"),
  strptime = strptime(largev, "%B %d,%Y"),
  times = 10
)

Which gives:

#Unit: seconds
#     expr      min       lq     mean   median       uq      max neval cld
#  as.Date 1.479891 1.480671 1.527838 1.483158 1.489222 1.863777    10  a 
# strptime 2.177625 2.183247 2.237732 2.255282 2.268452 2.272537    10   b

---

As per mentionned by @cory in the comments, use ?strptime to get the format codes:

• %B Full month name in the current locale. (Also matches abbreviated name on input.)
• %d Day of the month as decimal number (01–31).
• %Y Year with century. Note that whereas there was no zero in the original Gregorian calendar, ISO 8601:2004 defines it to be valid (interpreted as 1BC)

来源：https://stackoverflow.com/questions/37141431/r-convert-string-date-e-g-october-1-2014-to-date-format