Hi r-help-boun...@r-project.org napsal dne 19.03.2010 11:25:12:
> Hello all, > > As an example, consider the following dataframe > > > df<-data.frame(id=c("b","b","a","a","a"),ord=c(2,1,1,3,2)) > > dates<-as.Date(c("02/27/92", "02/27/92", "01/14/92", "02/28/92", "02/01/ > 92"),"%m/%d/%y") > > df$dates<-dates > > which was ordered with > > > df<-df[order(df$id,df$dates),] > > Now I would like to add a column containing a sequence (disregarding > ties) that represents the order of the variable > "dates" in each case of the variable "id", resulting in this dataframe: > > > seq.id<-c(1,2,3,1,2) > > df$seq.id<-seq.id > > id ord dates seq.id > 3 a 1 1992-01-14 1 > 5 a 2 1992-02-01 2 > 4 a 3 1992-02-28 3 > 1 b 2 1992-02-27 1 > 2 b 1 1992-02-27 2 Here is one option but I believe others will come with more clever one. df$seq.id<-unlist(tapply(as.numeric(df$id), df$id, order)) Regards Petr > > > Thanks in advance, > > Duarte Viana > > ______________________________________________ > 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.