Please, Gentlemen,
this whole thread has *nothing* to do with "R-devel",
and pretty much with "R-help".
So please revert to there (or do reply off-list if you really
want that)
Regards, Martin
>>>>> "TC" == Tony Chiang <[EMAIL PROTECTED]>
>>>>> on Wed, 28 May 2008 16:57:04 +0100 writes:
TC> Hi Martin, I think I was extremely unclear about my
TC> question. If I have a list of $n$ character vectors, I
TC> would like to look at the intersection of $k$ of these
TC> vectors (of which there are n choose k). Martin, you
TC> methods (at least the first one) is one that I use, but
TC> I also use the combn(n,k) and take the columns of the
TC> output to subset the original list for which to take the
TC> multiple intersections.
TC> Robert has pointed out (to me) that this might be a
TC> (hyper)graph function. While I agree that the list
TC> could be represented as hyper-edges, I also tend to
TC> think that it is a more general set theoretic
TC> issue. Personally, I am looking at some statistics on
TC> posets, and this comes up for me. But without any other
TC> suggestions, I will find out if I can incorporate a
TC> function into graph or hypergraph.
TC> Cheers, --tony
TC> On Wed, May 28, 2008 at 3:58 PM, Martin Morgan
TC> <[EMAIL PROTECTED]> wrote:
>> Hi Tony -- off-list, as I think you're looking for
>> something else...
>>
>> "Tony Chiang" <[EMAIL PROTECTED]> writes:
>>
>> > Hi all,
>> >
>> > I don't know if this is the correct venue for this
>> question, but I am sure > that someone will correct me if
>> I am in the wrong list.
>> >
>> > I have been searching throughout R for a function that
>> can find the > intersection of multiple sets of
>> "things". Say for instance, I have a list > of $n$
>> character vectors and would like to find the intersection
>> of all $k$ > subsets. I don't believe that there is such
>> a function to do this (or am I > wrong?). It is a pretty
>> easy to encode such a function...there was an e-mail >
>> about how a recursive function to intersect an arbitrary
>> number of sets > which is elegant and useful (sorry I
>> forgot the person's name who wrote the > 2 line
>> function).
>>
>> Maybe this is what you were thinking of?
>>
>> Intersect=function(x, ...) { if (length(list(...))>1)
>> Intersect(x, Intersect(...)) else intersect(x, ...) }
>>
>> > Intersect(letters[1:5], letters[3:6], letters[4:7]) [1]
>> "d" "e" > l=list(letters[1:5], letters[3:6],
>> letters[4:7]) > do.call("Intersect", l) [1] "d" "e"
>>
>> Also
>>
>> > Reduce(intersect, l, letters) [1] "d" "e"
>>
>> This won't be efficient for a large set of 'things', and
>> I'm not getting how n and k fit in -- 'all k subsets'
>> implies all elements of n?
>>
>> Martin
>>
>> > My question is two-fold:
>> >
>> > 1. If such a function already exists, what is it
>> called? > 2. If such a function does not exists, it is
>> worthwhile to encode it (i.e. > can I send my code to
>> someone?).
>> >
>> > Cheers, > --tony
>> >
>> > [[alternative HTML version deleted]]
>> >
>> > ______________________________________________ >
>> R-devel@r-project.org mailing list >
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>> --
>> Martin Morgan Computational Biology / Fred Hutchinson
>> Cancer Research Center 1100 Fairview Ave. N. PO Box
>> 19024 Seattle, WA 98109
>>
>> Location: Arnold Building M2 B169 Phone: (206) 667-2793
>>
[[alternative HTML version deleted]]
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