[R] data.frame - how to calculate the number of rows
Pfeiffer & Koberstein Immobilien GmbH - Ralf Pfeiffer
ralf.pfeiffer at pfeiffer-koberstein-immobilien.de
Wed Dec 26 20:08:12 CET 2007
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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