[R] data.frame - how to calculate the number of rows

[Henrique Dallazuanna]

If i understand your question, you can try this:

cbind(summaryBy(B+C~ A,  data=df,FUN=c(mean, var)), 'num
rows'=as.numeric(table(df$A)))

On 26/12/2007, Agrarimmobilien <ralf.pfeiffer at agrarimmobilien.info> wrote:
> Hello,
>
> I had to give some more information to my posting:
>
> as ouput there are more than one row, depending on the values of column A
> (transformierung to distinct values, here 3 and 4, but there are much more)
>
> >        A            B                C
> > 1      3             6                 5
> > 2      3             4                 20
> > 3      3             8                 2
> > 4      4             8                 3
> > 5      4             2                 6
>
> Output:
>
> >        A            B                C                      num rows
> > 1      3            6                 6.16                  3
> > 2      4            5                 4.00                  3
>
>
> B is mean and C variance.
>
>
> thank you
> Macki
>
>
>
> > Hello,
> >
> > it seems to be a simple problem, but  I couldn't find an answer in the
> > archiv. (I think, it must has something to do with the group-select, like
> > in
> > php)
> >
> > I've the following data.frame:
> >
> >        A            B                C
> > 1      3             6                 5
> > 2      4             4                 20
> > 3      5             8                 2
> >
> > I want to get the number of the rows in the 4th column, like:
> >
> >        A            B                C                      num rows
> > 1      3            6                 6.16                  3
> >
> >
> > (B is mean, C is variance by using summaryBy(B+C~ A,  data=daten,
> > FUN=c(mean,var))  from the doBy-package)
> >
> > But, how can I add the column 'numrow' and count the number of the rows?
> >
> > Thanks!
> >
> > Macki
> >
> > ______________________________________________
> > R-help at 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 at 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O