convert to date and strip time?

问题

I have some data that looks like this:

dates <- structure(c(1L, 2L, 4L, 3L), .Label = c("Sat, 18 Nov 2017 00:00:00 GMT", 
                                             "Thu, 16 Nov 2017 00:00:00 GMT", "Tue, 14 Nov 2017 00:00:00 GMT", 
                                             "Wed, 15 Nov 2017 00:00:00 GMT"), class = "factor")

I would like to convert it to a date format instead of having it as a factor. Additionally, I want to strip the 00:00:00 GMT because it is meaningless

I tried lubridate but I'm having troubles with the format:

library(lubridate)
mdy(dates)
Warning message:
All formats failed to parse. No formats found.

回答1:

This looks like it is working:

as.POSIXct(dates, format = '%a, %d %b %Y %H:%M:%S')
#[1] "2017-11-18 GMT" "2017-11-16 GMT" "2017-11-15 GMT" "2017-11-14 GMT"

回答2:

We can also use dmy_hms from the lubridate package.

library(lubridate)

dmy_hms(dates, tz = "GMT")
# [1] "2017-11-18 GMT" "2017-11-16 GMT" "2017-11-15 GMT" "2017-11-14 GMT"

回答3:

Use as.Date like this. It ignores junk at the end so this works. No packages are used.

as.Date(dates, "%a, %d %b %Y")
## [1] "2017-11-18" "2017-11-16" "2017-11-15" "2017-11-14"

来源：https://stackoverflow.com/questions/47366703/convert-to-date-and-strip-time