[R] ifelse strips POSIXct class from object

[Duncan Murdoch]

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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