Regular expression help

[Reese Crispen]

Hello,

Apologies for making a second regular expressions-related post today, but the topic is new to me and I've struggled to answer my current problem with the info online.

I have the following string values, say, for variable Branching:

st12a(5)==1 & st13b == 3
st8a(88) == 1
(e1 == 1  | e1 == 2) & e2==0

and I want to convert the (1 or 2-digit) number in the parentheses that may be followed by " ==" or "==" to two underscores and the number without parentheses :

st12a__5==1 & st13b == 3
st8a__88 == 1
(e1 == 1  | e1 == 2) & e2==0

(notice last value unchanged)


Any help?

Thanks a lot,
Reese

v 14.2

[William Lisowski]

* Example generated by -dataex-. To install: ssc install dataex
clear
input str28 text
"st12a(5)==1 & st13b == 3"    
"st8a(88) == 1"              
"(e1 == 1  | e1 == 2) & e2==0"
"st8a(88) != 1"              
end

generate str40 new = ustrregexra(text,"\((\d+)\)( *==)","__$1$2")
list, clean noobs

. list, clean noobs

                            text                            new  
        st12a(5)==1 & st13b == 3       st12a__5==1 & st13b == 3  
                   st8a(88) == 1                  st8a__88 == 1  
    (e1 == 1  | e1 == 2) & e2==0   (e1 == 1  | e1 == 2) & e2==0  
                   st8a(88) != 1                  st8a(88) != 1

Regarding documentation, to the best of my knowledge, only in the Statlist post linked here is it documented that Stata's new regular expression parser is the ICU regular expression engine documented at http://userguide.icu-project.org/strings/regexp.

[Reese Crispen]

So helpful--thanks again, William!