DAT <- 1:8
?apply
apply(DAT,mean)
?mapply
x <- as.data.frame(cbind(x1 = c(3,NA,12,7), x2 = c(4:1, 2:5)) )
dimnames(x)[[1]] <- letters[1:8]
apply(x, 2, mean, trim = .2,na.rm=TRUE)
?mean