On 18/11/2014 10:23 AM, Dennis Fisher wrote:
R 3.1.1
OS X
Colleagues
When I use the duplicated function, I often need to find both the duplicates
and the original element that was duplicated. This can be accomplished with:
duplicated(OBJECT) | duplicated(OBJECT, fromLast=TRUE)
From my perspective, an improvement in the duplicated function would be an
option that accomplishes this with a single call to the function. This could
either be:
1. a new option: all=TRUE (pick whatever name makes sense)
2. allowing fromLast to take a new value (e.g., NA, in the spirit of
the xpd option in par())
If my suggestion would yield unintended consequences, it can certainly be
ignored.
The duplicated() function is pretty fast, so what's wrong with your
original version? If you find it to be too much typing, wouldn't it be
simplest to write your own function, e.g.
nonunique <- function(x) duplicated(x) | duplicated(x, fromLast=TRUE)
?
Something I've wanted more than once is a variation on duplicated that
returns the index of the duplicated element, so for example
dupindex(c(7,7,7,2,3,2))
would return
0 1 1 0 0 4
or possibly
1 1 1 4 5 4
Duncan Murdoch
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