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

The specific problem OP is posting could also be solved by

tt[is.na(X), X := 0]