df1$ind <- ave(integer(nrow(df1)), df1$id, FUN=seq_along) There are faster ways to do this if you know that id is sorted.
Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of Peter Maclean > Sent: Wednesday, June 13, 2012 7:15 AM > To: R mailing list > Subject: Re: [R] Indexing Grouped Data > > I need help in indexing grouped data. In this excample (df1 data), the first > child had a > first immunization at age 2. The second child had the first, second and third > immunization > at age 5,10, and 12, the third child had first and second immunization at age > 4 and 6 and > the fourth child had the first immunization at age 2. I have df1 and I need > to create df2 > with and "ind' variable that indicate if the immunization is first, second or > third. Note that > the data is not balanced but is sorted such that the fisrt observation (of an > individual) is > the first immunization. > > > > df1 <- data.frame(id = c(1,2,2,2,3,3,4), age = c(4,5,10, 12, 4,6, 2), dose = > c(1.8,1.8,1.6,1.2,1.8,1.6,1.8)) > > > > df2 <- data.frame(id = c(1,2,2,2,3,3,4), age = c(4,5,10, 12, 4,6, 2), > > ind=c(1,1,2,3,1,2,1), > dose = c(1.8,1.8,1.6,1.2,1.8,1.6,1.8)) > > > > df1 > id age dose > 1 1 4 1.8 > 2 2 5 1.8 > 3 2 10 1.6 > 4 2 12 1.2 > 5 3 4 1.8 > 6 3 6 1.6 > 7 4 2 1.8 > > df2 > id age ind dose > 1 1 4 1 1.8 > 2 2 5 1 1.8 > 3 2 10 2 1.6 > 4 2 12 3 1.2 > 5 3 4 1 1.8 > 6 3 6 2 1.6 > 7 4 2 1 1.8 > > > > > Peter Maclean > Department of Economics > UDSM > [[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.
