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Re: st: editing string variables to remove letters and keep only numbers


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: editing string variables to remove letters and keep only numbers
Date   Tue, 18 Jun 2013 00:10:20 +0100

There are is a dedicated functions in -egenmore- (SSC) (-sieve()-)
but let's take it from first principles.

gen length = length(strvar)
su length, meanonly
local lmax = r(max)

gen numstr = ""
gen letterstr = ""

forval i = 1/`max' {
      replace numstr = numstr + substr(strvar, `i', 1) if
inrange(real(substr(strvar, `i', 1)), 0, 9)
      replace letterstr = letterstr + substr(strvar, `i', 1) if
!inrange(real(substr(strvar, `i', 1)), 0, 9)
}
Nick
njcoxstata@gmail.com


On 17 June 2013 23:53, Michael McCulloch <mm@pinestreetfoundation.org> wrote:
> I have a variable in my dataset that (due to changes in data entry practices over time) contains several styles of the variable ID:
>
>         - a number (e.g. 164)
>         - a letter-number combination (e.g. e64)
>         - a comma-separated letter-number combination (e.g. e64,e65)
>
> In seeking to (A) remove the letters, and (B) separate the comma-separated into two separate variables, ID1 and ID2, I wrote the following argument:
>
> . split ID, p(",")
> . gen str id1_new =""           // make new ID to separate out the "e" from ID
> . replace id1_new=substr(id1,2,3)
>
>
> This successfully splits ID into ID1 and ID2.
>
> This also works if:
>         a 3-digit variable has a preceding letter (e64 is changed to 64)
>
> However, in the case of a 3-digit values WITHOUT PRECEDING LETTER, the first digit is removed (164 is changed to 64).
>
> Any suggestions would be appreciated.
>
>
> Best wishes,
> Michael McCulloch, LAc MPH PhD
>
> --
> Pine Street Foundation, since 1989
> 124 Pine Street | San Anselmo | California | 94960-2674
> P: (415) 407-1357 | F: (206) 338-2391 | http://www.PineStreetFoundation.org
>
>
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