Just to explain my previous mail, here is the output I get. > dim(tissue.exp) [1] 1532 20 > pick<-sample(tissue.exp,5,replace=TRUE) > dim(pick) [1] 1532 5 > tissue.exp.t<-t(tissue.exp) > dim(tissue.exp.t) [1] 20 1532 > pick<-sample(tissue.exp.t,5,replace=TRUE) > dim(pick) NULL -------- Thanks ../Murli