NA in data.table

Question

I have a data.table that contains some groups. I operate on each group and some groups return numbers, others return NA. For some reason data.ta

Answer 1

you can also do something like this :

dtb <- data.table(a=1:10)

mat <- ifelse(dtb == 9,NA,dtb$a)

The above command will give you matrix but you can change it back to data.table

new.dtb <- data.table(mat)
new.dtb
     a
 1:   1
 2:   2
 3:   3
 4:   4
 5:   5
 6:   6
 7:   7
 8:   8
 9:  NA
10:  10

Hope this helps.