"autonumber" for grouping variable
say 'dat' is your data frame, then one way is the following: f <- factor(dat$Id, levels = unique(dat$Id)) dat$Number <- unclass(f) dat I hope it helps. Best, Dimitris
clion wrote:
Dear R users, my dataframe looks like this head(dat) Id sex byear age 1 300 m 2003 50 2 300 m 2003 36 3 402 f 2003 29 4 402 f 2003 21 5 402 f 2003 64 6 150 m 2005 43 ... ...(where Id is just the Identification number of Individual, sex (male or female), byear (=birthyear)) now, I 'd like to add a column, where each Individual gets an automated number starting from 1, so that I can number them consecutively something which should look like this: Id sex byear age Number 1 300 m 2003 50 1 2 300 m 2003 36 1 3 402 f 2003 29 2 4 402 f 2003 21 2 5 402 f 2003 64 2 6 150 m 2005 43 3 ... ... how can I easily do this? thanks a lot for any help, Birte
Dimitris Rizopoulos Assistant Professor Department of Biostatistics Erasmus University Medical Center Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands Tel: +31/(0)10/7043478 Fax: +31/(0)10/7043014