Here is one way of doing it:

> 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$dates<-dates
> df$seq <- ave(as.numeric(df$dates), df$id, FUN=order)
> df
  id ord      dates seq
1  b   2 1992-02-27   1
2  b   1 1992-02-27   2
3  a   1 1992-01-14   1
4  a   3 1992-02-28   3
5  a   2 1992-02-01   2


On Fri, Mar 19, 2010 at 6:25 AM, Duarte Viana <viana.sptd@gmail.com> wrote:

> 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
>
>
> Thanks in advance,
>
> Duarte Viana
>
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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