# [R] Simple question on finding duplicates

David L Carlson dcarlson at tamu.edu
Wed Jul 25 22:25:26 CEST 2012

```Minor correction:

duplicate <- ifelse(c(0, a\$col[-length(a\$col)])==a\$col, 1, 0)

-------
David

> -----Original Message-----
> From: David L Carlson [mailto:dcarlson at tamu.edu]
> Sent: Wednesday, July 25, 2012 3:23 PM
> To: 'Jeff'; 'r-help at r-project.org'
> Subject: RE: [R] Simple question on finding duplicates
>
> duplicate <- ifelse(c(0, a\$col[-length(a\$col)])==c(a\$col), 1, 0)
>
> ----------------------------------------------
> David L Carlson
> Associate Professor of Anthropology
> Texas A&M University
> College Station, TX 77843-4352
>
>
> > -----Original Message-----
> > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> > project.org] On Behalf Of Jeff
> > Sent: Wednesday, July 25, 2012 3:06 PM
> > To: r-help at r-project.org
> > Subject: [R] Simple question on finding duplicates
> >
> >
> >    I'm  trying  to find duplicate values in a column of a data frame.
> > For
> >    example, dataframe (a) below has two 3's. I would like to mark
> each
> > value of
> >    each row as either not being a duplicate of the one before (0), or
> > as a
> >    duplicate (1) - for example, as in dataframe (b). In SPSS, I would
> > simply
> >    compare each value to it's "lagged" value, but I can't figure out
> > how to do
> >    this with R.
> >    Can someone point me in the right direction?
> >    Thanks
> >    a <- data.frame( col1 = c(1,2,3,3,4))
> >    b <- data.frame( col1 = c(1,2,3,3,4), duplicate = c(0,0,0,1,0))
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help