On Aug 3, 2011, at 2:45 AM, Liviu Andronic wrote:
Hello David
On Tue, Aug 2, 2011 at 4:14 PM, David Winsemius <dwinsem...@comcast.net
> wrote:
x <- data.frame(a = as.Date('2000-01-01'), b=as.Date('2001-01-01'))
x$d <- x$a -x$b
require(mefa)
rep(x, 2)
a b d
1 2000-01-01 2001-01-01 -366
2 2000-01-01 2001-01-01 -366
str(rep(x,2))
'data.frame': 2 obs. of 3 variables:
$ a: Date, format: ...
$ b: Date, format: ...
$ d: num -366 -366 # notice that a difftime object has lost its
class
Nice catch. Thanks for pointing it out.
# Whereas using the [rep(. , .) , ] approach does preserve the
difftime
class.
str(x[rep(1,2) , ])
'data.frame': 2 obs. of 3 variables:
$ a: Date, format: ...
$ b: Date, format: ...
$ d:Class 'difftime' atomic [1:2] -366 -366 # leap year
.. ..- attr(*, "units")= chr "days"
The above is nice. I wouldn't have thought of it.
Since that works out of the box with fewer potential side-effects,
I am not
sure a new method is needed.
Your solution still seems more like an obscure side-effect of
subsetting than an intuitive feature, in the sense that before trying
it out the average user would probably first turn to base::rep() when
in need to replicate a df, and then (perhaps) to
mefa:::rep.data.frame() (with all the associated confusion and
pitfalls). I would tend to believe that if there is a clean R-ish way
to implement a base::rep.data.frame() it could still be useful.
To me that _is_ the R-ish way. It did not seem at all obscure.
Duplicating column numbers also a way to replicate columns or
rearrange them:
Try:
xtest=data.frame(a=letters[1:10], b=1:10)
xtest[ , c(1,2,2,1)]
--
David.
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