[R] counting entries in vector

Dimitris Rizopoulos d.rizopoulos at erasmusmc.nl
Wed Feb 4 17:08:21 CET 2009

try this:

k <- c("bb", "bb", "bb", "aa", "cc", "cc")

f <- factor(k, levels = unique(k))

you can put it in one line but it's less readable. I hope it helps.


axionator wrote:
> Hi all,
> I've a vector with entries, which are all of the same type, e.g. string:
> k <- c("bb", "bb", "bb", "aa", "cc", "cc")
> and want to create a second vector containing the number of each entry
> in k in the same order as in k, i.e.
> c(3, 1, 2)
> or:
> k <- c(5,5,5,5,2,2,4)
> => c(4,2,1)
> thanks
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Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
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