c.POSIXct

No one answered this so I submitted it to the bugs system and there I
got the response that it is documented behavior; however, whether its
documented or not is hardly the point -- its undesirable that tzone is
lost when using c.

That's one man's opinion - from docs 

  if you want to specify an object in a particular timezone but
   to be printed in the current timezone you may want to remove the
   ?"tzone"? attribute (e.g. by ?c(x)?).

so apparently that is a design choice and hence I doubt it can be changed as it would break code that uses that feature. As many things in R whether it was a good choice is up for debate but it has been made already. (Think about how you would combine different times with different tzones - there is no "right" way to do so and thus stripping is very plausible and consistent)

Cheers,
Simon
On Thu, Aug 12, 2010 at 11:33 AM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
Currently if x1 and x2 are POSIXct then c(x1, x2) will not have a
tzone attribute even if x1 or x2 or both do but it should.

This could be fixed with the following c.POSIXct:

c.POSIXct <- function (..., recursive = FALSE) {
       tzones <- lapply(list(...), attr, which = "tzone")
       lengths <- sapply(tzones, length)
       if (any(lengths > 1)) stop("tzone cannot have length greater than 1")
       which <- sapply(tzones, length) == 1
       tzone <- unique(unlist(tzones[which]))
       if (length(tzone) != 1) tzone <- NULL
structure(c(unlist(lapply(list(...), unclass))), class = c("POSIXt",
   "POSIXct"), tzone = tzone)
}

# test
x1 <- Sys.time()
x2 <- structure(x1, tzone = "UTC")
x3 <- structure(x1, tzone = "other")

# these all currently give NULL but with
# above give indicated value

attr(c(x1, x1), "tzone") # NULL
attr(c(x2, x2), "tzone") # "UTC"
attr(c(x1, x2), "tzone") # "UTC"
attr(c(x2, x1), "tzone") # "UTC"
attr(c(x1, x2, x3), "tzone") # NULL

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c.POSIXct

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