Loop through data.table and create new columns basis some condition

Question

I have a data.table with quite a few columns. I need to loop through them and create new columns using some condition. Currently I am writing separate line of condition for

Answer 1

For completeness, it should be noted that dplyr's mutate_each provides a handy way of tackling such problems:

library(dplyr)

result <- DT %>%
    group_by(town,tc) %>%
    mutate_each(funs(mean,sd,
                     uplimit = (mean(.) + 1.96*sd(.)),
                     lowlimit = (mean(.) - 1.96*sd(.)),
                     Aoutlier = as.integer(. >= mean(.) - 1.96*sd(.) &
                                               . <= mean(.) - 1.96*sd(.))),
                -town,-tc)