Dear r-users,

Basically, I have a data as follows,

> data
       S s1 s2 s3 s4 s5      prob obs num.strata
1  NNNNN  N  N  N  N  N 0.0000108  32       <NA>
2  NNNNY  N  N  N  N  Y 0.0005292  16       <NA>
3  NNNYN  N  N  N  Y  N 0.0005292  24       <NA>
4  NNNYY  N  N  N  Y  Y 0.0259308   8          1
....

I want to replace <NA> by 0, when I tried the following command, I get som
error message.
data[is.na(data)]<-0

Warning message:
In `[<-.factor`(`*tmp*`, thisvar, value = 0) :
  invalid factor level, NAs generated

Anyone knows how to deal with this?

Thanks,

Kate

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