R help - Dec 2008 - stuck with repeated values

R Gurus,I have a vector of nearly 90,000 characters from which I have to
extract the index of the characters which are repeated. So suppose if
x<-c("a","a","b","a","b","c","d")
then my output would be a vector having
the index where the values are repeated i.e (1,2,3,4,5). I have been able to
isolate out the values that are repeated from the unique list of characters
in x (i.e. y<-c("a","b")). One method can be to use a
loop on the which
function but that would be too time consuming. Any hint on using the apply
function effectively would be useful
Thanks and Regards
Souvik Bandyopadhyay
Lecturer,
Dept of Biostatistics,
Indian Institute of Public Health,
Hyderabad

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On 12/3/2008 6:32 AM, SOUVIK BANDYOPADHYAY wrote:
> R Gurus,I have a vector of nearly 90,000 characters from which I have to
> extract the index of the characters which are repeated. So suppose if
>
x<-c("a","a","b","a","b","c","d")
then my output would be a vector having
> the index where the values are repeated i.e (1,2,3,4,5). I have been able
to
> isolate out the values that are repeated from the unique list of characters
> in x (i.e. y<-c("a","b")). One method can be to use
a loop on the which
> function but that would be too time consuming. Any hint on using the apply
> function effectively would be useful
> Thanks and Regards
x <-
c("a","a","b","a","b","c","d")

duplicated(x)
[1] FALSE  TRUE FALSE  TRUE  TRUE FALSE FALSE

x %in% x[duplicated(x)]
[1]  TRUE  TRUE  TRUE  TRUE  TRUE FALSE FALSE

which(x %in% x[duplicated(x)])
[1] 1 2 3 4 5

?duplicated
> Souvik Bandyopadhyay
> Lecturer,
> Dept of Biostatistics,
> Indian Institute of Public Health,
> Hyderabad
> 
> 	[[alternative HTML version deleted]]
> 
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