stata - Drop a specific character from string responses

Question

I have a string variable and some of the responses have an extra character at the beginning. The character in question is a constant character in all cases. The variable is ICD-code. For example, instead of G23 I have DG23.

Is there a way in Stata to remove the excess D character?

My data looks like this

ID	diag
1	DZ456
2	DG32
3	DY258
4	DD35
5	DS321
6	DD21
7	DA123

Answer 1

For basic information in this territory, consult help string functions.

* Example generated by -dataex-. To install: ssc install dataex
clear
input byte d str5 diag
1 "DZ456"
2 "DG32" 
3 "DY258"
4 "DD35" 
5 "DS321"
6 "DD21" 
7 "DA123"
end

replace diag = substr(diag, 2, .) if substr(diag, 1, 1) == "D"

list 

     +----------+
     | d   diag |
     |----------|
  1. | 1   Z456 |
  2. | 2    G32 |
  3. | 3   Y258 |
  4. | 4    D35 |
  5. | 5   S321 |
     |----------|
  6. | 6    D21 |
  7. | 7   A123 |
     +----------+