CODEWITHSUNDEEP
r
jd123
jd123

Reputation: 147

Turn vector of dates into workable data frame

I have a vector dates with elements in the same format, like element 1 "Mon, 05 Sep 2013 01:19:18 -0000" . I am trying to turn this vector into a data frame so I can manipulate them. For instance, I would like to be able to subtract 4 days from the first entry and get "Thu, 01 Sep 2013 01:19:18 -0000". I would also like to plot each element on a time line.

I have tried 

as.Date(dates,'%a, %d %b %z %H:%M:%S %z')

and

for (d in dates){ 
    as.Date(d,'%a, %d %b %z %H:%M:%S -%z')
}

but I always get NA.

Upvotes: 1

Views: 63

Answers (1)

Mikko
Mikko

Reputation: 7755

You were very close. Try:

dates <- c("Mon, 05 Sep 2013 01:19:18 -0000", "Thu, 01 Sep 2013 01:19:18 -0000")    
strptime(dates, '%a, %d %b %Y %H:%M:%S %z')

You just had a typo in the year argument (should be %Y, not %z). If you want to store the time as a date, add as.Date as you have done

as.Date(dates, '%a, %d %b %Y %H:%M:%S %z')

If you want to make a data.frame and subtract 4 days from each date, try:

data.frame(date = strptime(dates, '%a, %d %b %Y %H:%M:%S %z'), 
subtracted = strptime(dates, '%a, %d %b %Y %H:%M:%S %z') - as.difftime(4, unit="days"))

Note that R returns your system-specific times, which might differ from the times in your vector as specified by the %z argument (see ?strptime).

Upvotes: 1

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