How to determine if date is a weekend or not (not using lubridate)

Question

I have a vector of date objects (yyyy-mm-dd) and I want to determine if any of them are on weekend or not. Is there a function that can determine this straighta

Answer 1

The wday in both lubridate and data.table (yes, data.table has pretty much everything but the kitchen sink :-) both do a variation on:

as.POSIXlt(x, tz = tz(x))$wday + 1 # lubridate
as.POSIXlt(x)$wday + 1L            # data.table

So you could, in theory, just do:

as.POSIXlt("2014-10-18")$wday + 1
## [1] 7

and then test for the weekend days as other answer(s) do.