Increment a date by some time period

Question

When using the "+" operator to increment a date (or date-time), how do i specify that the increment is in days (or months, or weeks, or years)?

> Sys.Date()
[1] "2013-08-23"
> Sys.Date() + 1
[1] "2013-08-24"
> ISOdate(2013,8,23)
[1] "2013-08-23 12:00:00 GMT"
> ISOdate(2013,8,23) + 1
[1] "2013-08-23 12:00:01 GMT"

Answer 1

Use lubridate::days

> require(lubridate)
> Sys.Date()
[1] "2013-08-23"
> Sys.Date() + days(1)
[1] "2013-08-24"
> ISOdate(2013, 8, 23)
[1] "2013-08-23 12:00:00 GMT"
> ISOdate(2013, 8, 23) + days(1)
[1] "2013-08-24 12:00:00 GMT"

With lubridate, you can also use years(), seconds(), etc., or define your own duration.

Answer 2

You could use seq for some basic calculations:

today = Sys.Date()
fiveWeeksAhead = tail(seq(today, by = 'week', length = 5), 1)

Or use a package like lubridate if you need more advanced functions.