[R] unique deletes names - intended?
tuechler at gmx.at
Wed Jul 5 14:31:19 CEST 2006
Thank you for your clarification.
At 11:04 05.07.2006 +0100, Prof Brian Ripley wrote:
>On Tue, 4 Jul 2006, Heinz Tuechler wrote:
>> Dear All,
>> as shown in the example, unique() deletes names of vector elements.
>> Is this intended?
>Yes. Think of the vector as a set: it is supposed to immaterial which of
>the duplicated elements is retained.
>The help page says
> An object of the same type of 'x'. but if an element is equal to
> one with a smaller index, it is removed.
>so it is starting with a new object, not 'x'. However, the array method
>works differently, so the documentation needs clarification.
>> Of course, one can use indexing by !duplicated() instead.
>Be careful, as you might get a method for [ and that might not do want you
>intended (e.g. for a time series).
>> ## unique deletes names
>> v1 <- c(a=1, b=2, c=3, e=2, a=4)
>> unique(v1) # names deleted
>> v1[!duplicated(v1)] # names preserved
>> platform i386-pc-mingw32
>> arch i386
>> os mingw32
>> system i386, mingw32
>> status Patched
>> major 2
>> minor 3.1
>> year 2006
>> month 07
>> day 01
>> svn rev 38471
>> language R
>> version.string Version 2.3.1 Patched (2006-07-01 r38471)
>> R-help at stat.math.ethz.ch mailing list
>> PLEASE do read the posting guide!
>Brian D. Ripley, ripley at stats.ox.ac.uk
>Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
>University of Oxford, Tel: +44 1865 272861 (self)
>1 South Parks Road, +44 1865 272866 (PA)
>Oxford OX1 3TG, UK Fax: +44 1865 272595
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