From: jim holtman <jholtman_at_gmail.com>

Date: Sat 23 Sep 2006 - 12:55:05 GMT

*> unlist(mapply(seq, x[,1], x[,2]))
*

[1] 2 3 4 5 7 8 9 15 16 17 18 19 20

*>
*

Date: Sat 23 Sep 2006 - 12:55:05 GMT

try this:

*> x <- rbind(c(2,5), c(7,9), c(15,20))
**> x
*

[,1] [,2]

[1,] 2 5 [2,] 7 9 [3,] 15 20

[1] 2 3 4 5 7 8 9 15 16 17 18 19 20

On 9/23/06, George W. Gilchrist <gwgilc@wm.edu> wrote:

> I have a very large dataframe and wish to extract a subset of rows. I

*> have a two column matrix listing the starting and ending indices of
**> one subset on each row. My idea is to create a vector of indices that
**> could be applied to the dataframe and I have a solution using a for
**> loop (below). But surely there is some more elegant way to do this! I
**> looked thorough the archives without success. Thanks for any ideas.
**>
**> > tmp1 <- matrix(c(2,5,7,9,15,20), 3,2, byrow=T)
**> > tmp1
**> [,1] [,2]
**> [1,] 2 5
**> [2,] 7 9
**> [3,] 15 20
**> > t.ind <- NULL
**> > for (i in 1:3) t.ind <- c(t.ind, seq(tmp1[i,1], tmp1[i,2]))
**> > t.ind
**> [1] 2 3 4 5 7 8 9 15 16 17 18 19 20
**> >
**>
**> cheers, George
**>
**> ..................................................................
**> George W. Gilchrist Email: gwgilc@wm.edu
**> Director of Graduate Studies Phone: (757) 221-7751
**> Department of Biology, Box 8795 Fax: (757) 221-6483
**> College of William & Mary
**> Williamsburg, VA 23187-8795
**> http://gwgilc.people.wm.edu/
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
**> and provide commented, minimal, self-contained, reproducible code.
**>
*

-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Sat Sep 23 22:59:29 2006

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