sample() takes a prob = argument which lets you supply weights, which need not sum to one so, if I understand you, you could just pass TRUEs and FALSEs for those rows you want. If I'm wrong about that last bit, I'm still pretty confident sample(prob = ) is the way to go.
Best, Michael On Thu, Jun 14, 2012 at 6:02 AM, Guido Leoni <guido.le...@gmail.com> wrote: > Dear list I wish to extract from a population genotypized for 10 SNP a > subsample of the same population of size n with similar allele frequencies. > Essentially i have a matrix of 200 rows (df) like this > Name,Condition,rs1385699_X,rs6625163_X,rs962458_X,Rs4658627_1, > sample01,Case,1,1,1,-1 > sample02,Control,1,1,1,1 > sample06,Control,1,-1,1,0 > sample10,Case,1,1,1,0 > sample11,Control,1,1,1,1 > sample24,Control,-1,-1,1,0 > sample29,Control,1,-1,1,0 > sample42,Case,-1,-1,1,0 > sample64,Case,-1,1,1,0 > .... > I'm interested to mantain in my subsample the same frequencies of those > observed for the 1 value in each column > I approached the problem with sample() function > > mysample<-df[sample(1:nrow(df),100,replace=F),] > Then I tested that the frequencies of each allele in mysample are not > statistically different respect to the initial dataset by mean of prop.test > This seems to work but do you know if there is a package that can do the > same thing allowing for example a more strict control? > Thank you very much > Guido > > [[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. ______________________________________________ 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.
