[R] ifelse strips POSIXct class from object
Duncan Murdoch
murdoch.duncan at gmail.com
Sun Jun 5 14:39:17 CEST 2011
On 11-06-05 8:23 AM, Denis Chabot wrote:
> Hi,
>
> I was "losing" my dates in a script and upon inspection, found that my recent switch from separate "if" and "else" to "ifelse" was the cause. But why?
See ?ifelse. The class of the result is the same as the class of the
test, not the classes of the alternatives. You need to manually attach
the class again, or use a different construction.
Duncan Murdoch
>
> my.date = as.POSIXct("2011-06-04 08:00:00")
> default.date = seq(as.POSIXct("2011-01-01 08:00:00"), as.POSIXct("2011-09-01 08:00:00"), length=15)
> x = 4 * 60 * 60
> (my.date + x)
> (min(default.date) + x)
> (new.date = ifelse(!is.na(my.date), my.date + x, min(default.date) + x) )
>
> (if(!is.na(my.date)) new.date2 = my.date + x else new.date2= min(default.date) + x )
>
> On my machine, new.date is "numeric" whereas new.date2 is "POSIXct" and "POSIXt", as desired.
>
> sessionInfo()
> R version 2.13.0 (2011-04-13)
> Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
>
> locale:
> [1] fr_CA.UTF-8/fr_CA.UTF-8/C/C/fr_CA.UTF-8/fr_CA.UTF-8
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
>
> Thanks in advance,
>
> Denis
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