**From:** Douglas Bates (*bates@stat.wisc.edu*)

**Date:** Sat 15 May 2004 - 04:52:59 EST

**Next message:**Prof Brian Ripley: "Re: [R] Tagging identical rows of a matrix"**Previous message:**Liaw, Andy: "RE: [R] Tagging identical rows of a matrix"**In reply to:**Scott Waichler: "[R] Tagging identical rows of a matrix"**Next in thread:**Prof Brian Ripley: "Re: [R] Tagging identical rows of a matrix"**Reply:**Prof Brian Ripley: "Re: [R] Tagging identical rows of a matrix"

Message-id: <6r1xlmj0xg.fsf@bates4.stat.wisc.edu>

Scott Waichler <scott.waichler@pnl.gov> writes:

*> I would like to generate a vector having the same length
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*> as the number of rows in a matrix. The vector should contain
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*> an integer indicating the "group" of the row, where identical
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*> matrix rows are in a group, and a unique row has a unique integer.
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*> Thus, for
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*>
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*> a <- c(1,2)
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*> b <- c(1,3)
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*> c <- c(1,2)
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*> d <- c(1,2)
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*> e <- c(1,3)
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*> f <- c(2,1)
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*> mat <- rbind(a,b,c,d,e,f)
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*>
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*> I would like to get the vector c(1,2,1,1,2,3). I know dist() gives
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*> part of the answer, but I can't figure out how to use it for
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*> this purpose without doing a lot of looping. I need to apply this
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*> to matrices up to ~100000 rows.
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I believe you want to start with unique which, when applied to a

matrix, provides the unique rows.

*> unique(mat)
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[,1] [,2]

a 1 2

b 1 3

f 2 1

I'm sure others will be able to provide clever ways of doing the

matching against the unique rows.

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**Next message:**Prof Brian Ripley: "Re: [R] Tagging identical rows of a matrix"**Previous message:**Liaw, Andy: "RE: [R] Tagging identical rows of a matrix"**In reply to:**Scott Waichler: "[R] Tagging identical rows of a matrix"**Next in thread:**Prof Brian Ripley: "Re: [R] Tagging identical rows of a matrix"**Reply:**Prof Brian Ripley: "Re: [R] Tagging identical rows of a matrix"

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