Tena koe Whitney tapply should work. Try:
tapply(yourData$IndividualID, yourData$FamilyID, sample, size=1) # untested HTH .... Peter Alspach -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Whitney Melroy Sent: Friday, 28 March 2014 10:11 a.m. To: r-help@r-project.org Subject: [R] Select random observation from a group Hello, I have a dataset with family data. For an analysis, I need to select one subject per family at random. Here is an example of what my data look like: FamilyID IndividualID DadID MomID Sex 1 101 103 104 1 1 102 103 104 2 1 103 0 0 1 1 104 0 0 2 2 201 202 203 1 2 202 202 203 2 2 203 202 203 1 2 204 202 203 2 I want to randomly select ONE subject for each family (there are roughly 2300 families) and make a new dataframe. Here is what I tried so far, with no success: Uniq.fam.id<-df[unique(df$FamilyID),] Uniq.fam.id <- df[sample(unique(df$FamilyID)),] Uniq.fam<-unique(df$FamilyID) Uniq.fam.id <- df[sample(Uniq.fam),] I would be eternally grateful for any help. Thanks, Whitney ______________________________________________ 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. The contents of this e-mail are confidential and may be ...{{dropped:14}} ______________________________________________ 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.
