Find string before different types of symbols

[James Lee]

Hi Statalist community,

I have a sample dataset below. It comprises of all the different ways that participants describe their race.

* Example generated by -dataex-. To install: ssc install dataex
clear
input str123 Race
"African American/Black"                                                                                                    
"White                         "                                                                                            
"I do not wish to answer."                                                                                                  
"African American/Black,Hawaiian/Other Pacific Islander"                                                                    
"Asian "                                                                                                                    
"American Indian/Alaskan Native"                                                                                            
"African American/Black,American Indian/Alaskan Native"                                                                      
"African American/Black,American Indian/Alaskan Native,White                         "                                      
"African American/Black,White                         "                                                                      
"American Indian/Alaskan Native,White                         "                                                              
"African American/Black,Asian "                                                                                              
"White                         ,American Indian/Alaskan Native"                                                              
"White                         ,Hawaiian/Other Pacific Islander"                                                            
"African American/Black,I do not wish to answer."                                                                            
"African American/Black,American Indian/Alaskan Native,Hawaiian/Other Pacific Islander"                                      
"Asian ,White                         "                                                                                      
"American Indian/Alaskan Native,African American/Black,Asian ,White                         "                                
"American Indian/Alaskan Native,Asian "                                                                                      
"African American/Black,Asian ,Hawaiian/Other Pacific Islander"                                                              
"White                         ,African American/Black"                                                                      
"Hawaiian/Other Pacific Islander"                                                                                            
"Hawaiian/Other Pacific Islander,White                         "                                                            
"African American/Black,American Indian/Alaskan Native,Asian ,Hawaiian/Other Pacific Islander,White                         "
"African American/Black,American Indian/Alaskan Native,Asian "                                                              
"African American/Black,American Indian/Alaskan Native,Asian ,White                         "                                
"Asian ,Hawaiian/Other Pacific Islander"                                                                                    
"American Indian/Alaskan Native,Asian ,White                         "                                                      
"African American/Black,American Indian/Alaskan Native,Hawaiian/Other Pacific Islander,White                         "      
"American Indian/Alaskan Native,Hawaiian/Other Pacific Islander,White                         "                              
"White                         ,I do not wish to answer."                                                                    
"Hawaiian/Other Pacific Islander,African American/Black"                                                                    
"African American/Black,Asian ,White                         "                                                              
"African American/Black,Asian ,Hawaiian/Other Pacific Islander,White                         "                              
"American Indian/Alaskan Native,Hawaiian/Other Pacific Islander"                                                            
"White                         ,African American/Black,American Indian/Alaskan Native,Hawaiian/Other Pacific Islander"      
end

You can see that some individuals list multiple races. I want the first race in an individual's record. I was using the link below and used the suggested code.

https://www.statalist.org/forums/for...rt-of-a-string

In my situation, I have different types of symbols such as "/" and "," and "." and trailing blanks. So I wrote the following code but the syntax is wrong. Is there something that I'm missing. Thanks for your help.

gen wanted = substr(Race, 1, strpos(Race, "/" | "," |"." | " ") - 1)

[Hemanshu Kumar]

Consider this:

gen wanted = ustrtrim(ustrregexs(1)) if ustrregexm(Race,"^([a-zA-Z\s]+)")

which produces:

  +----------------------------------------------------------------------+
  | Race                                                          wanted |
  |----------------------------------------------------------------------|
  | African American/Black                              African American |
  | White                                                          White |
  | I do not wish to answer.                     I do not wish to answer |
  | African American/Black,Hawaiian/Other Pa..          African American |
  | Asian                                                          Asian |
  | American Indian/Alaskan Native                       American Indian |
  | African American/Black,American Indian/A..          African American |
  | African American/Black,American Indian/A..          African American |
  | African American/Black,White            ..          African American |
  | American Indian/Alaskan Native,White    ..           American Indian |
  | African American/Black,Asian                        African American |
  | White                         ,American ..                     White |
  | White                         ,Hawaiian/..                     White |
  | African American/Black,I do not wish to ..          African American |
  | African American/Black,American Indian/A..          African American |
  | Asian ,White                                                   Asian |
  | American Indian/Alaskan Native,African A..           American Indian |
  | American Indian/Alaskan Native,Asian                 American Indian |
  | African American/Black,Asian ,Hawaiian/O..          African American |
  | White                         ,African A..                     White |
  | Hawaiian/Other Pacific Islander                             Hawaiian |
  | Hawaiian/Other Pacific Islander,White   ..                  Hawaiian |
  | African American/Black,American Indian/A..          African American |
  | African American/Black,American Indian/A..          African American |
  | African American/Black,American Indian/A..          African American |
  | Asian ,Hawaiian/Other Pacific Islander                         Asian |
  | American Indian/Alaskan Native,Asian ,Wh..           American Indian |
  | African American/Black,American Indian/A..          African American |
  | American Indian/Alaskan Native,Hawaiian/..           American Indian |
  | White                         ,I do not ..                     White |
  | Hawaiian/Other Pacific Islander,African ..                  Hawaiian |
  | African American/Black,Asian ,White     ..          African American |
  | African American/Black,Asian ,Hawaiian/O..          African American |
  | American Indian/Alaskan Native,Hawaiian/..           American Indian |
  | White                         ,African A..                     White |
  +----------------------------------------------------------------------+

My regular expression looks for a permitted set of characters from the start of the string, which includes alphabets (lower and uppercase) and whitespace. I think this should work well for you, if all the strings are in English.

[James Lee]

@Hemanshu Kumar

Thank you so much. This is exactly what I want. Is possible for you to explain what the following code does? I can't even decipher this but it does exactly what I want. Thanks again.

 
 ^([a-zA-Z\s]+

[Hemanshu Kumar]

It might be helpful for you to go through some discussions of regular expressions. A couple good places to start might be Asjad Naqvi's post here or Rose Ann Madeiros' slides here.

To break down the exact pattern I used:

^ says look for this pattern at the start of the string
( ) say the substring that matches the pattern contained within these parentheses is something that I will reference -- this is what will be picked up by the ustrregexs(1)
[] say match with anything within these square brackets
a-z matches with any lowercase alphabet
A-Z matches with any uppercase alphabet
\s matches with a whitespace
+ matches with one or more instances of whatever precedes it, in this case, any of the stuff within the [], that is to say, any number of lower and uppercase alphabets and whitespaces (but nothing else!)

I also like to use the website https://regex101.com/ to test my regular expressions before using them.

[James Lee]

@Hemanshu Kumar

Thank you so much for the resources. This explains so much. I appreciate your help. Thanks again.