[R] Intersection of more than two groups in one function?

[Berton Gunter]

No, I know of no "canned" way to do it, as it's based on match(), which is
for two vectors only.

A brute force loop to do it is simple, as I suspect you realize. Perhaps a
faster way is to use tabulate() to find values that appear n times (for n
vectors). That is:

## assume your integer vectors are components of a list, mylist.

## warning: not tested
bigvec<-unlist(mylist)
sort(unique(bigvec))[tabulate(bigvec)==length(mylist)]



-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Ken Termiso
> Sent: Thursday, May 05, 2005 1:15 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Intersection of more than two groups in one function?
> 
> Hi all,
> 
> As far as I can tell, the only canned way to do an intersect 
> between two 
> vectors of ints is the intersect(vec1, vec2) function -- is 
> there another 
> function I'm missing for intersecting more than two vectors??
> 
> TIA,
> Ken
> 
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