Re: [Rd] 'data.frame' method for base::rep()

From: Martin Maechler <maechler_at_stat.math.ethz.ch>
Date: Wed, 03 Aug 2011 14:44:20 +0200

>>>>> David Winsemius <dwinsemius_at_comcast.net> >>>>> on Tue, 2 Aug 2011 10:14:59 -0400 writes:

    > On Aug 2, 2011, at 7:55 AM, Liviu Andronic wrote:

>> Dear R developers Would you consider adding a
>> 'data.frame' method for the base::rep function? The need
>> to replicate a df row-wise can easily arise while
>> programming, and rep() is unable to handle such a
>> case. See below.

    >>> x <- iris[1, ]

>>

    > x[ rep(1,2), ] # "works"

Yes, indeed, and that I think is my "definitive" answer to the proposal.
Defining a rep() method for data frames seems much less sensible First because one simple "substitute" exists (namely indexing, see above), and to me, not the least because there are several problems / questions that would have to be answered

  --> and of course, the indexing solution

     xx <- iris[ rep(1:nrow(iris), 3) , ]  

  does implement one sensible way of producing unique row.names,   {though, I must say, not the "optimal" one if the issue is efficiency}

Rather keep using [,] and let's not get into having to maintain yet another data.frame method ..

Martin Maechler, ETH Zurich



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