[R] Simple question on finding duplicates

[David L Carlson]

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

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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))
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