[R] stuck with repeated values

[Chuck Cleland]

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
> 
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> 
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-- 
Chuck Cleland, Ph.D.
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