Does the following work for you?
> df2 <- transform(df, ObsID=ave(rep(0,length(Group)), Group,
FUN=seq_along))
> head(df2)
Value Group ObsID
1 -0.0025132 B 1
2 -1.2456156 A 1
3 -2.0531704 B 2
4 1.5861770 B 3
5 0.1900908 A 2
6 0.7197067 B 4
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 Robert Baer
> Sent: Monday, May 09, 2011 2:22 PM
> To: R-help@r-project.org
> Subject: [R] Creating Observation ID
>
> If I have a data frame something like:
> Value=rnorm(30)
> Group = sample(c('A','B','C'), 30, replace=TRUE)
> df = data.frame(Value, Group)
>
> It seems like it should be simple to create an 'ObsID' column
> which indicates the observation order of each Value within
> each of the 3 groups. Somehow, I can't quite see how to do
> it without manually sub-setting the parent data frame and
> then putting it back together again.
>
> Anyone able to get me started on a cleaner (more R-like) approach?
>
> Thanks,
>
> Rob
>
> ------------------------------------------
> Robert W. Baer, Ph.D.
> Professor of Physiology
> Kirksville College of Osteopathic Medicine
> A. T. Still University of Health Sciences
> 800 W. Jefferson St.
> Kirksville, MO 63501
> 660-626-2322
> FAX 660-626-2965
>
> [[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.
>
______________________________________________
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.
