Hi Silvano, How about this?
id <- seq(80) weight <- runif(80) # randomize 4 groups with 'sample' function group <- sample(rep(seq(4),20)) dat <- cbind(id, weight, group) # ordered dataset by group res <- data.frame(dat[order(group),]) # get mean and variance for each group aggregate(res$weight, list(group=res$group), mean) aggregate(res$weight, list(group=res$group), var) Cheers, Charles On Fri, Aug 23, 2013 at 9:03 AM, Silvano <silv...@uel.br> wrote: > Hi, > > I have a set of 80 animals and their respective weights. I would like > create 4 groups of 20 animals so that the groups have means and variances > with values ??very close. > How can I make this randomization in R? > > Thanks, > > ------------------------------**-------- > Silvano Cesar da Costa > Departamento de EstatÃstica > Universidade Estadual de Londrina > Fone: 3371-4346 > > ______________________________**________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help> > PLEASE do read the posting guide http://www.R-project.org/** > posting-guide.html <http://www.R-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > -- Charles Determan Integrated Biosciences PhD Candidate University of Minnesota [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org 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.
