R help - May 2010 - intersect() without discarding duplicates?

Hi all,
   The ?intersect entry kindly points out that it discards duplicate
entries.  I'm looking, however, to get the intersection while KEEPING
duplicate entries, and there are no instructions on how to accomplish this
using intersect().

Does anybody have any idea how this might be done, or am I going to need to
program something from scratch (something like ordering the vectors and then
looping through them)?



ex:
> a <- c(2,4,2,3)
> b<-c(6,6,5,2,2,8,4)
> intersect(a,b)
[1] 2 4



I'd hope the answer to be 2 2 4.

Regards,
Jonathan

	[[alternative HTML version deleted]]

On May 20, 2010, at 5:58 PM, Jonathan wrote:
> Hi all,
>   The ?intersect entry kindly points out that it discards duplicate
> entries.  I'm looking, however, to get the intersection while KEEPING
> duplicate entries, and there are no instructions on how to  
> accomplish this
> using intersect().
>
> Does anybody have any idea how this might be done, or am I going to  
> need to
> program something from scratch (something like ordering the vectors  
> and then
> looping through them)?
>
>
>
> ex:
>
>> a <- c(2,4,2,3)
>> b<-c(6,6,5,2,2,8,4)
>> intersect(a,b)
> [1] 2 4
 > b %in% a
[1] FALSE FALSE FALSE  TRUE  TRUE FALSE  TRUE

# Now use logical indexing on "b"

 > b[b %in% a]
[1] 2 2 4
>
>
>
> I'd hope the answer to be 2 2 4.
>
> Regards,
> Jonathan
>
> 	[[alternative HTML version deleted]]
>
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