Here is one way of doing it:
> x <- read.table(textConnection("CFISCA FIRMS
YEAR VAR VALUE
+ 20345 nike 2005 EC01 34
+ 20345 nike 2006 EC01 45
+ 56779 mediaset 2005 EC01 65
+ 64568 agazzini 2005 EC01 78
+ 64568 agazzini 2006 EC01 56
+ 78907 uniteam 2006 EC01 46"),
header=TRUE)
> closeAllConnections()
> # split by FIRMS and only keep those that have two entries
> result <- do.call(rbind, lapply(split(x, x$FIRMS), function(.firm){
+ if (nrow(.firm) != 2) return(NULL)
+ else return(.firm)
+ }))
>
> result
CFISCA FIRMS YEAR VAR VALUE
agazzini.4 64568 agazzini 2005 EC01 78
agazzini.5 64568 agazzini 2006 EC01 56
nike.1 20345 nike 2005 EC01 34
nike.2 20345 nike 2006 EC01 45
>
On Wed, Apr 21, 2010 at 10:32 AM, n.via...@libero.it <n.via...@libero.it>wrote:
>
> Dear list,
> >I have a question about the selection of Variables in dataframes.
> >I have a dataframes like this:
> >
> >CFISCA FIRMS YEAR VAR VALUE
> >20345 nike 2005 EC01 34
> >20345 nike 2006 EC01 45
> >56779 mediaset 2005 EC01 65
> >64568 agazzini 2005 EC01 78
> >64568 agazzini 2006 EC01 56
> >78907 uniteam 2006 EC01 46
> >
> >
> >what my result should be is a new dataframes which have only firms which
> have
> >data in both years (2005,2006)
> >
> >CFISCA FIRMS YEAR VAR VALUE
> >20345 nike 2005 EC01 34
> >20345 nike 2006 EC01 45
> >64568 agazzini 2005 EC01 78
> >64568 agazzini 2006 EC01 56
> >
> >
> >Thanks for your attention!!!
>
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
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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
What is the problem that you are trying to solve?
[[alternative HTML version deleted]]
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