Re: select rows which have at least a given number of duplicates

[David L Lorenz <lorenz@usgs.gov>]

Vincent,
  The tabulate() function will
convert anything to factors and process those data correctly. It is the
subsetting [m$X] that must be integer. 
  You can use the by() function
and do.call("rbind", ) to do what you want:

do.call("rbind", by(m, m$X,
function(x) if(nrow(x) > 2) x else NULL))

  Take a look at the documentation
for the functions to see what they do.
Dave

"vincent vinh-hung" <conrvhgv@az.vub.ac.be>
Sent by: s-news-owner@lists.biostat.wustl.edu

09/29/2006 08:23 AM

To	<s-news@lists.biostat.wustl.edu>
cc
Subject	[S] select rows which have at least a given number of duplicates

I would like to select rows from a table that 
have at least, say, 3 duplicates.

> m <- as.data.frame(c(1,1,4,3,2,3,1))
> m$Y <-c("a","b","c","d","e","f","g")
> names(m) <- c("X","Y")
> m
  X Y 
1 1 a
2 1 b
3 4 c
4 3 d
5 2 e
6 3 f
7 1 g

Command tabulate seems to do the job:
> m[tabulate(m$X)[m$X]>2,]
  X Y 
1 1 a
2 1 b
7 1 g

But tabulate is limited to integers.
Are there other ways that could be applied to reals
or to text?

Thanks in advance for any suggestion.

Vincent Vinh-Hung


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