> On 23 Dec 2014, at 10:05 , Martin Maechler <maech...@stat.math.ethz.ch> wrote:
>
>
> In cases like this one when the condition 'Cond' is a
> simple TRUE or FALSE (i.e. of length 1), using
>
> if(Cond) A else B
>
> instead of
>
> ifelse(Cond, A, B)
>
> is
>
> 1. much more R - like [[ "everything you do is a function call" ]]
> hence much more elegant
>
> 2. considerably more efficient.
>
> 3. :-) less typing: uses two "," less ;-)
>
4. Considerably less confusing in terms of the class of the result.
> ifelse (TRUE, Sys.Date(), as.Date("2014-1-1") )
[1] 16427
> ifelse (FALSE, Sys.Date(), as.Date("2014-1-1") )
[1] 16071
> if (TRUE) Sys.Date() else as.Date("2014-1-1")
[1] "2014-12-23"
> if (FALSE) Sys.Date() else as.Date("2014-1-1")
[1] "2014-01-01"
(S/R made the Solomonic decision to take the class of the result of ifelse()
from the _condition_ part, which is the only possibility common to both cases,
but most likely also something that noone would ever actually want.)
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
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