Hello! I have a data set with 8 columns and in about 5000 rows. What I want to do is to generate samples of this data set. Samples of a special size, as example 200. What is the easiest way to do this? No special things are needed, only the random selection of 200 rows of the data set. Thanks Alex -- Alexander Geisler * Kaltenbach 151 * A-6272 Kaltenbach email: alexander.geisler at gmx.at | alexander.geisler at gmail.com phone: +43 650 / 811 61 90 | skpye: al1405ex
?sample should tell you what you need to know. On 26/11/06, Alexander Geisler <alexander.geisler at gmail.com> wrote:> Hello! > > I have a data set with 8 columns and in about 5000 rows. What I want to > do is to generate samples of this data set. > > Samples of a special size, as example 200. > > What is the easiest way to do this? No special things are needed, only > the random selection of 200 rows of the data set. > > Thanks > Alex > > -- > Alexander Geisler * Kaltenbach 151 * A-6272 Kaltenbach > email: alexander.geisler at gmx.at | alexander.geisler at gmail.com > phone: +43 650 / 811 61 90 | skpye: al1405ex > > ______________________________________________ > R-help at 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. >-- ================================David Barron Said Business School University of Oxford Park End Street Oxford OX1 1HP
split <- sample(2,nrow(dataframe),replace=T,prob=c(0.04,0.96)) dataframe[split==1,] # 200 dataframe[split==2,] # 4800 regards, christian> ?sample should tell you what you need to know. > > On 26/11/06, Alexander Geisler <alexander.geisler at gmail.com> wrote: > >> Hello! >> >> I have a data set with 8 columns and in about 5000 rows. What I want to >> do is to generate samples of this data set. >> >> Samples of a special size, as example 200. >> >> What is the easiest way to do this? No special things are needed, only >> the random selection of 200 rows of the data set. >> >> Thanks >> Alex >> >> -- >> Alexander Geisler * Kaltenbach 151 * A-6272 Kaltenbach >> email: alexander.geisler at gmx.at | alexander.geisler at gmail.com >> phone: +43 650 / 811 61 90 | skpye: al1405ex >> >> ______________________________________________ >> R-help at 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. >> >> > > >
Further to Alexander's question ... could anyone provide assistance with random stratified sampling? Let's say we have Alex's dataframe and we want to stratify the random selection by group membership (which is contained in one of the eight columns). We might want to randomly select: 1) a constant number (e.g., 5) of rows from each group, or 2) a percentage (e.g. 10%) of rows from each group resulting in groups being represented proportionally in the sample (with respect to the population). I am aware of stratsrs but this function does not seem to allow the second of the above two options. Any ideas how to achieve this in R? Thanks, Mark On 11/26/06, Alexander Geisler <alexander.geisler at gmail.com> wrote:> Hello! > > I have a data set with 8 columns and in about 5000 rows. What I want to > do is to generate samples of this data set. > > Samples of a special size, as example 200. > > What is the easiest way to do this? No special things are needed, only > the random selection of 200 rows of the data set. > > Thanks > Alex > > -- > Alexander Geisler * Kaltenbach 151 * A-6272 Kaltenbach > email: alexander.geisler at gmx.at | alexander.geisler at gmail.com > phone: +43 650 / 811 61 90 | skpye: al1405ex > > ______________________________________________ > R-help at 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. >