[R] compute new variable

[Matthias von Rad]

Hello,
maybe my question ist stupid, but I would like to calculate a new  
variable for all cases in my dataset. Inspired by the dialog in Rcmdr  
I tried
Datenmatrix$cohigha<- with(Datenmatrix,mean (c(M2ORG, M5ORG, M8ORG,  
M11ORG), na.rm = TRUE)
as output I got the same number for all my cases (possibly the  
overallmean of all cases), instead of a mean for each case.
Can you help me with this problem?
regards
Matthias