Help with data management please

#1
Hi,
I have a dataset that are all string and missing data are as NA. I am trying to convert it to numeric with encode command. I don't know how to convert the NA to . (before encoding or after) and with which command?
Thanks
 
#2
Hi,
I have a dataset that are all string and missing data are as NA. I am trying to convert it to numeric with encode command. I don't know how to convert the NA to . (before encoding or after) and with which command?
Thanks

Now, I have sorted my problem to some extent. I transferred the excel to STATA and generated new variables with encode which then all became numeric. Some variables were as 1,2,3 where 3 was missing data and I could change it to .,missing, with mvdecode.
For some other variables the missing data is as NA and STATA reads then as numeric. I am stuck how to change them to ., missing.
SOS