Converting string to numeric in Stata

Run help encode and you can read:

Do not use encode if varname contains numbers that merely happen to be stored as strings; instead, use generate newvar = real(varname) or destring; see real() or [D] destring.

For example:

clear all
set more off

input id str5 age
1 "32"
2 "14"
3 "65"
4 "54"
5 "98"
end

list

encode age, gen(age2)
destring age, gen(age3)

list, nolabel

Note the difference between using encode and destring. The former assigns numerical codes (1, 2, 3, ...) to the string values, while destring converts the string value to numeric. This you see stripping the value labels when you list:

. list, nolabel

     +------------------------+
     | id   age   age3   age2 |
     |------------------------|
  1. |  1    32     32      2 |
  2. |  2    14     14      1 |
  3. |  3    65     65      4 |
  4. |  4    54     54      3 |
  5. |  5    98     98      5 |
     +------------------------+

A simple list or browse may confuse you because encode assigns the sequence of natural numbers but also assigns value labels equal to the original strings:

. list

     +------------------------+
     | id   age   age3   age2 |
     |------------------------|
  1. |  1    32     32     32 |
  2. |  2    14     14     14 |
  3. |  3    65     65     65 |
  4. |  4    54     54     54 |
  5. |  5    98     98     98 |
     +------------------------+

The nolabel option shows the "underlying" data.

You mention it is inconsistent, but for future questions posting exact input and results is more useful for those trying to help you.

Try taking a look at this method? Sounds like you may have slipped up somewhere in your method.