Replacing all missing values in R data.table with a value

Question

If you have an R data.table that has missing values, how do you replace all of them with say, the value 0? E.g.

aa = data.table(V1=1:10,V2=c(1,2,2,3,3,3,4,4,         


        

Answer 1

I would make use of data.table and lapply, namely:

tt[,lapply(.SD,function(kkk) ifelse(is.na(kkk),-666,kkk)),.SDcols=names(tt)]

yielding in:

V1    X V2
 1:  1 -666  1
 2:  2 -666  2
 3:  3    a  2
 4:  4    b  3
 5:  5    c  3
 6:  6    d  3
 7:  7 -666  4
 8:  8 -666  4
 9:  9 -666  4
10: 10 -666  4