[R] Filter out some levels?

[Christian Schulz]

Hi ,

how is it possible t cut some levels from one factor to  subsetting  a 
data.frame on?

subdata <- subset(data, data$FACTOR="1" | 
data$FACTOR="BETA" | data$FACTOR="XY")
???

Maybe a modifcation here is better, but how?
mergex[mergex$PLZX %in% levels(mergex$PLZX) ,]


Many thanks and regards,
Christian