[R] Aggregate by First case

[Moshe Olshansky]

If df is your dataframe, try

aggregate(df$Year,list(df$Id),min)


--- On Fri, 30/5/08, Jojje Andersson <dietaamigo at hotmail.com> wrote:

> From: Jojje Andersson <dietaamigo at hotmail.com>
> Subject: [R] Aggregate by First case
> To: "r-help at r-project.org" <r-help at r-project.org>
> Received: Friday, 30 May, 2008, 5:13 PM
> Hello!
>  
> I have an maybe a to a simple question but I cant get it
> right.
>  
> I have a dataframe with in one column an id-variable and in
> another a year-variable. One id-number can occur several
> years.
> I have sorted the dataframe on id then on year so the same
> id-number is sorted by year with the first occurens at top.
>  
> Now I want to make a subset of this dataframe with just the
> first year the id-number occur, so the first case of every
> id.
>  
> Id         Year
> 123456 2001
> 123456 2002
> 123456 2003
> 655432 2001
> 655432 2002
> 655432 2003
>  
> Is there a simple command I can do?
>  
> Thanks!
>  
> Jojje
>  
>  
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