[R] data.frame - how to calculate the number of rows
Agrarimmobilien
ralf.pfeiffer at agrarimmobilien.info
Wed Dec 26 20:44:50 CET 2007
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
>
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