amy, here is a piece of code copied from my blog, which might answer part of your question.
library(MASS); data(Boston); # DIVIDE DATA INTO TESTING AND TRAINING SETS set.seed(2005); test.rows <- sample(1:nrow(Boston), 100); test.set <- Boston[test.rows, ]; train.set <- Boston[-test.rows, ]; On 2/18/07, Amy Whitehead <[EMAIL PROTECTED]> wrote: > Hi, > > I am looking for a way to randomly extract a specified number of rows from a > data frame. I was planning on binding a column of random numbers to the > data frame and then sorting the data frame using this bound column. But I > can't figure out how to use this column to sort the entire data frame so > that the content of the rows remains together. Does anyone know how I can > do this? Hints for other ways to approach this problem would also be > appreciated. > > Cheers > Amy > > > Amy Whitehead > School of Biological Sciences > University of Canterbury > Private Bag 4800 > Christchurch > Ph 03 364 2987 ext 7033 > Cellphone 021 2020525 > Email [EMAIL PROTECTED] > > ______________________________________________ > 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. > -- WenSui Liu A lousy statistician who happens to know a little programming (http://spaces.msn.com/statcompute/blog) ______________________________________________ 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.