> You may not have expected it, but that result is what is described: From the
> help page for `as.vector`:
>
> "For as.vector, a vector (atomic or of type list). All attributes are removed
> from the result if it is of an atomic mode, ..."
>
> And since POSIXct vectors _are_ of atomic mode, all of their attributes are
> removed.
It is not that simple: as.vector is a generic function and may have methods
written for certain classes (just
as with as.list). It does have a method for factor (which has an atomic mode)
> methods("as.vector")
[1] as.vector.factor
so we get some attributes copied
> f <- factor(c("Anteater","Bear","Cat"))
> str(f)
Factor w/ 3 levels "Anteater","Bear",..: 1 2 3
> str(as.vector(f, mode="list"))
List of 3
$ : Factor w/ 3 levels "Anteater","Bear",..: 1
$ : Factor w/ 3 levels "Anteater","Bear",..: 2
$ : Factor w/ 3 levels "Anteater","Bear",..: 3
Since there is no POSIXct method we get the default behavior.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of David Winsemius
> Sent: Wednesday, May 22, 2013 1:52 PM
> To: Alexandre Sieira
> Cc: r-help@r-project.org
> Subject: Re: [R] as.vector with mode="list" and POSIXct
>
>
> On May 20, 2013, at 2:09 PM, Alexandre Sieira wrote:
>
> > I was trying to convert a vector of POSIXct into a list of POSIXct,
> > However, I had a
> problem that I wanted to share with you.
> >
> > Works fine with, say, numeric:
> >
> >
> >> v = c(1, 2, 3)
> >> v
> > [1] 1 2 3
> >> str(v)
> > num [1:3] 1 2 3
> >> l = as.vector(v, mode="list")
> >> l
> > [[1]]
> > [1] 1
> >
> > [[2]]
> > [1] 2
> >
> > [[3]]
> > [1] 3
> >
> >> str(l)
> > List of 3
> > $ : num 1
> > $ : num 2
> > $ : num 3
> >
> > If you try it with POSIXct, on the other hand...
> >
> >
> >> v = c(Sys.time(), Sys.time())
> >> v
> > [1] "2013-05-20 18:02:07 BRT" "2013-05-20 18:02:07 BRT"
> >> str(v)
> > POSIXct[1:2], format: "2013-05-20 18:02:07" "2013-05-20 18:02:07"
> >> l = as.vector(v, mode="list")
> >> l
> > [[1]]
> > [1] 1369083728
> >
> > [[2]]
> > [1] 1369083728
> >
> >> str(l)
> > List of 2
> > $ : num 1.37e+09
> > $ : num 1.37e+09
> >
> > The POSIXct values are coerced to numeric, which is unexpected.
>
> You may not have expected it, but that result is what is described: From the
> help page for
> `as.vector`:
>
> "For as.vector, a vector (atomic or of type list). All attributes are removed
> from the result
> if it is of an atomic mode, ..."
>
> And since POSIXct vectors _are_ of atomic mode, all of their attributes are
> removed.
>
> > is.atomic(as.POSIXct("2001-01-01") )
> [1] TRUE
>
> (I realize that this is a belated response, and that you and Jeff Newmiller
> are continuing a
> correspondence on what I think appears to be a separate concern) , but I
> needed to go
> back to the first posting to figure out what the questions were.
>
> >
> > The documentation for as.vector says: "The default method handles 24 input
> > types and
> 12 values of type: the details of most coercions are undocumented and subject
> to
> change." It would appear that treatment for POSIXct is either missing or needs
> adjustment.
>
> As in the case of factor-classed vectors, POSIXct-vectors are atomic mode.
> Yours was a
> selective reading. (And you found a way around this with `as.list`.)
>
> > is.atomic(factor("2001-01-01") )
> [1] TRUE
> --
> David.
> >
> > Unlist (for the reverse) is documented to converting to base types, so I
> > can't complain.
> Just wanted to share that I ended up giving up on vectorization and writing
> the two
> following functions:
> >
> >
> > unlistPOSIXct <- function(x) {
> > retval = rep(Sys.time(), length(x))
> > for (i in 1:length(x)) retval[i] = x[[i]]
> > return(retval)
> > }
> >
> > listPOSIXct <- function(x) {
> > retval = list()
> > for (i in 1:length(x)) retval[[i]] = x[i]
> > return(retval)
> > }
> >
> > Is there a better way to do this (other than using *apply instead of for
> > above) that
> better leverages vectorization? Am I missing something here?
> >
> > Thanks!
> >
> >
> --
>
> David Winsemius
> Alameda, CA, USA
>
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