generating a new variable if strings match certain characters

[Nick Richardson]

Hello,

I have a dataset that contains information on 28 different drugs (variables drug1-drug28) and their positivity levels, but these are string variables currently. see below for an example:

* Example generated by -dataex-. For more info, type help dataex
clear
input str33(drug1 drug2 drug3 drug4) str34 drug5
"Tramadol (94.78)"                  " Benzoylecgonine (125)"            " Cocaine (0)"                     ""                              ""                                  
"Tramadol (95.426)"                 ""                                  ""                                 ""                              ""                                  
"Tramadol (96.38)"                  " THC (4.57)"                       ""                                 ""                              ""                                  
"meta-Hydroxycocaine (Hair) (18.8)" " para-Hydroxycocaine (Hair) (6.4)" " Carboxy-THC (Hair) (2.46)"       " Benzoylecgonine (Hair) (218)" " ortho-Hydroxycocaine (Hair) (2.8)"
"meta-Hydroxycocaine (Hair) (4.9)"  " Norfentanyl (Hair) (24)"          " EDDP (Hair) (1421)"              " Benzoylecgonine (Hair) (773)" " ortho-Hydroxycocaine (Hair) (4.7)"
"para-Hydroxycocaine (Hair) (11)"   " Cocaethylene (Hair) (113)"        " meta-Hydroxycocaine (Hair) (14)" " Carboxy-THC (Hair) (2.11)"    " Benzoylecgonine (Hair) (604)"     
end

What i want to do is create a separate variable for each drug type that returns a value of 1 if drug1-drug28 contains the following characters "(0)". I've tried, for example,

gen result=regexm(drug1, "(0)")

, but this will return a value of 1 if 0 shows up anywhere. In the example above, in the first observation, "Cocaine (0)" should return a value of 1, but in the last observation, " Benzoylecgonine (Hair) (604)" should NOT return a value of 1.

Thank you for any assistance in syntax you can provide.

[Andrew Musau]

Include word boundaries. For these, you need Unicode regular expressions.

gen result3=ustrregexm(drug3, "\b(0)\b")

Res.:

. l drug3 result3, sep(0)

     +--------------------------------------------+
     |                            drug3   result3 |
     |--------------------------------------------|
  1. |                      Cocaine (0)         1 |
  2. |                                          0 |
  3. |                                          0 |
  4. |        Carboxy-THC (Hair) (2.46)         0 |
  5. |               EDDP (Hair) (1421)         0 |
  6. |  meta-Hydroxycocaine (Hair) (14)         0 |
     +--------------------------------------------+

.

[Nick Richardson]

Thanks so much, Andrew. Now im thinking that for my purposes, it might be better if that instead of generating a new variable set to 1, that instead, drug3 is set to missing if "(0)" appears. Would you know the syntax to do this?

[Andrew Musau]

replace drug3 ="" if ustrregexm(drug3, "\b(0)\b")