pos01 <- read.csv("pos_items.csv") pos_items.csv # modify the original dataset with some trick additives pos01$trseq <- c(1:149639) + (rnorm(1)*1000) - (rnorm(1)*300) pos01$trseq <- as.numeric( substr(as.character(pos01$trseq),1,3))+1000000 pos01$trseq <- substr(as.character(pos01$trseq),5,6) q01 <- sort(sample(unique(pos01$itemid), 50 )) q02 <- c("1","2", "3..