Chuck Cleland wrote: > Wadud, Zia wrote: >> Hi >> I have a panel dataset with large number of groups and differing number >> of observations for each group. I want to randomly select say, 20% of >> the groups or 200 groups, but along with all observations from the >> selcted groups (with the corresponding data). >> I guess it is possible to generate a random sample from the groups ids >> and then match that with the entire dataset to have the intended >> dataset, but it sounds cumbersome and possibly there is an easier way to >> do this? checked the package 'sampling' or command 'sample', but they >> cant do exactly the same thing. >> I was wondering if someone on this list will be able to share his/her >> knowldege? > > How about something like this? > > df <- data.frame(GROUP = rep(1:5, c(2,3,4,2,2)), Y = runif(13)) > > # Sample Two of the Five Groups > > subset(df, GROUP %in% with(df, sample(unique(GROUP), 2)))
The with() part can be dropped too. subset(df, GROUP %in% sample(unique(GROUP), 2)) >> Thanks in advance, >> Zia >> ********************************************************** >> Zia Wadud >> PhD Student >> Centre for Transport Studies >> Department of Civil and Environmental Engineering >> Imperial College London >> London SW7 2AZ >> Tel +44 (0) 207 594 6055 >> >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> [email protected] 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. -- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 512-0171 (M, W, F) fax: (917) 438-0894 ______________________________________________ [email protected] 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.
