Creating a dummy variable that checks if the substring of common ids is the sa e

[Julian Bausch]

Hi
I need to clean data in doing so I need to create a dummy variable. I want to see if for common ids the first 4 letters of the zip are similar or not
here a small example what I want to let the dummy do:

id	zip	dummy	..
1	12345	1
1	12344	1
2	12332	0
2	12342	0

I would be super nice if somebody could help me.
Best,
JB

[Carlo Lazzaro]

Julian:
welcome to this forum.
You may want to try:

input id zip
1 12345   
1 12344    
2 12332    
2 12342
end

. tostring zip, g(string_zip)

. gen wanted=substr(string_zip,1,4)

. bysort id: gen dummy=1 if wanted[_N]== wanted[_N-1]


. bysort id: replace dummy=0 if wanted[_N]!= wanted[_N-1]


. list

     +----------------------------------------+
     | id     zip   string~p   wanted   dummy |
     |----------------------------------------|
  1. |  1   12345      12345     1234       1 |
  2. |  1   12344      12344     1234       1 |
  3. |  2   12332      12332     1233       0 |
  4. |  2   12342      12342     1234       0 |
     +----------------------------------------+

.