Hi:
Is something like this what you were after?
x <- data.frame(A = sample(LETTERS[1:5], 1000, replace = TRUE),
B = rpois(1000, 50),
C = rnorm(1000))
x[unique(x$A), ]
A B C
4 E 49 1.18424176
5 B 51 0.51911271
1 D 71 0.06266016
2 E 61 0.59862609
3 A 45 0.55970798
x[unique(x$B), ] is a bit longer so is not included :)
HTH,
Dennis
On Thu, Oct 28, 2010 at 11:29 AM, boshao zhang <zbos...@yahoo.com> wrote:
> Dear everyone in the Mailing list:
>
> It is easy to get the unique elements in a column. But I would like to get
> rid of those rows that the elements of this column are redundant. Or
> sometimes, to have a look at the rows that the elements of this column are
> redundant is also important. I guess it boils down to throw out the index of
> the redundant elements.
>
> With millions of rows, how can I efficiently perform the task?
>
> Thank you in advance.
>
> Boshao
>
>
>
> [[alternative HTML version deleted]]
>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
