unique deletes names - intended?

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).

Greetings,
Heinz

## 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)

-- 
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)
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