[R] extract rows in dataframe with duplicated column values

[Marc Schwartz]

Here's one more possibility:

> subset(x, a %in% a[duplicated(a)])
  a  b
2 2 10
3 2 10
4 3 10
5 3 10
6 3 10

HTH,

Marc Schwartz


On Thu, 2005-03-17 at 22:25 -0500, Liaw, Andy wrote:
> OK, strike one...
> 
> Here's my second try:
> 
> > cnt <- table(x[,1])
> > v <- as.numeric(names(cnt[cnt > 1]))
> > v
> [1] 2 3
> > x[x[,1] %in% v, ]
>   a  b
> 2 2 10
> 3 2 10
> 4 3 10
> 5 3 10
> 6 3 10
> 
> Andy
> 
> > From: Liaw, Andy
> > 
> > Does this work for you?
> > 
> > > x[table(x[,1]) > 1,]
> >   a  b
> > 2 2 10
> > 3 2 10
> > 5 3 10
> > 6 3 10
> > 
> > Andy
> > 
> > > From: Tiago R Magalhaes
> > > 
> > > Hi
> > > 
> > > I want to extract all the rows in a data frame that have duplicates 
> > > for a given column.
> > > I would expect this question to come up pretty often but I have 
> > > researched the archives and surprisingly couldn't find anything.
> > > The best I can come up with is:
> > > 
> > > x <- data.frame(a=c(1,2,2,3,3,3), b=10)
> > > xdup1 <- duplicated(x[,1])
> > > xdup2 <- duplicated(x[,1][nrow(x):1])[nrow(x):1]
> > > xAllDups <- x[(xdup1+xdup2)!=0,]
> > > 
> > > This seems to work, but it's so convoluted that I'm sure there's a 
> > > better method.
> > > Thanks for any help and enlightenment
> > > 	[[alternative HTML version deleted]]
> > > 
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