How can I extract a part of a string variable which contains zipcode information?

[Shruti Sheopurkar]

Hello,
I'm working with Massachusetts zip code data and there are 3 kinds of formats the data is currently in:
1) Normal 5 digit zip code data, for example, 02144
2) 4 digit zip code, where the initial 0 is missing, for example, 2144
3) Zip code data of the format 02144-1234

My zip code variable is currently a string variable because of the "-" in the "02144-1234". I am hoping, with some help, to make the following transformations:
1) Add a 0 to the 4 digit zipcodes so that 2144 becomes 02144
2) Extract the first 5 digits from the "02144-1234" format zip code so that it becomes 02144.

I'm making these transformations so that I am able to destring the zip codes once they are all in the 5 digit zip code format (Ex: 02144).

I would appreciate any help I can get. Here's an extract from my data:

* Example generated by -dataex-. To install: ssc install dataex
clear
input str10 zip
"2140"     
"2148"     
"02121"     
"2151"     
"02121-2936"
"02119-3302"
"02140"     
"02136-3407"
"02301"     
"02150-3151"
"02122-1023"
"01905-2844"
"02124-2710"
"02108-4704"
"02121-1105"
"02121-1897"
"02122-1130"
"02301-1228"
"02148-7911"
"02368-4422"
"02151-5227"
"02143"     
"02125"     
"01905"     
"2149"     
"02148-2704"
"02368-1701"
"02127-3733"
"02150-3865"
"02151-2230"
"02125-1826"
"01760-5711"
"02145-1414"
"02119-1261"
"01905"     
"01905-1626"
"01902-3816"
"02148-5718"
"02130-2307"
"02143-4338"
"02170-3206"
"02121-1830"
"02151-2854"
"02131-2020"
"02151-4159"
"02148-7813"
"02145-1726"
"02151"     
"02119-3364"
"02125-3293"
"02126-2458"
"02150-2908"
"02135"     
"02148"     
"02145-1718"
"02139-3910"
"02128-1454"
"02151-2533"
"02151-3201"
"02121-2070"
"02151-5531"
"02368-1528"
"02128-2518"
"01702-6084"
"02124"     
"02149-5213"
"02148-4617"
"02145-1621"
"02145-3016"
"02130-1533"
"02139-4173"
"02149-4923"
"02126-2316"
"02130-2634"
"02368-3853"
"02472"     
"02148-2847"
"01902-2843"
"02136-2114"
"01902-1829"
"02151-2618"
"02150"     
"02119"     
"02155-5473"
"02120-1706"
"02150-3418"
"02131-1831"
"02145-2946"
"01902"     
"02150-3518"
"02148-4112"
"02128-1337"
"02125"     
"02121"     
"02126-2006"
"02128-2553"
"02301-5913"
"02150"     
"02150-2908"
"02124-1304"
"02151-2948"
"02150-1429"
"01902-3984"
"02151"     
"02368"     
"02140-3239"
"02136-6724"
"02072-2452"
"02150-3104"
"02124-2836"
"02124-3411"
"02129-2737"
"02125"     
"02128-1056"
"02136"     
"02150-3309"
"02150-3315"
"02302-2843"
"02124-1547"
"02127-2014"
"02476-6206"
"02119-1262"
"02150-1924"
"02302-3502"
"01903-2090"
"02151-4531"
"02135-4429"
"02148-1500"
"02141"     
"02119-1190"
"02169-5734"
"02151-4021"
"02129-2308"
"02118-1502"
"02124-2428"
"02118-2459"
"02121-1536"
"02472-3057"
"02128-2563"
"02126-1417"
"02130-1413"
"02149-5213"
"02122"     
"02131"     
"02148-2804"
"02136"     
"02169-7217"
"02121-3930"
"02122-3301"
"02130"     
"02151"     
"02150-3728"
"02148-7023"
"02151"     
"02170-3428"
"02150-2862"
"02150-2959"
"02122-1369"
"02149-3824"
"02124-4805"
"01887"     
"02119"     
"02149"     
"02126"     
"02145"     
"02215"     
"02155"     
"02126"     
"02118"     
"02136"     
"02119"     
"01901"     
"02127"     
"02135"     
"01905"     
"01902"     
"02118"     
"02149"     
"02150"     "     
"02121"     
"02119"     
"2151"     
"2125"     
"2130"     
"2186"     
"2152"     
"2151"     
"2124"     
"2149"     
"1905"     
end

Thank you in advance!

[Justin Niakamal]

Try

gen zipcode = zip 
replace zipcode = "0" + zipcode if length(zipcode) <= 4
replace zipcode = substr(zipcode,1,5)
destring zipcode, replace

[Oded Mcdossi]

Here's one way to go:

g zipn=substr(zip,1,5)
replace zipn=cond(length(zipn)==4,"0"+zipn,zipn)

Added: crossed with #2

[Joseph Mawa]

I hope this helps

replace zip = "0" + zip if length(zip)==4
replace zip = substr(zip,1,5) if length (zip)> 5

[Shruti Sheopurkar]

Thank you!