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st: Re: recoding question


From   "Joseph Coveney" <jcoveney@bigplanet.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: recoding question
Date   Tue, 25 Dec 2012 02:12:39 +0900

Peter Lachenbruch wrote:

I have a string variable with codes 
Markedly Improved
Markedly Worse
Moderately Improved
Moderately Worse
Slightly Improved
Slightly Worse
Unchanged

I want to convert these to a numeric variable, but ordered in terms of
improvement.  I was looking for a way to do this easily in one step, but didn't
find a simple command like encode or recode.  I ended up using encode to get the
variables numeric and then recoding them.  
Is there a simple way to do this?   For seven categories it's no big deal, but
if I had 20 categories and needed to do this repeatedly, it would be a pain.  
Another option would be to prefix a numeral for the codes but that seems
clumsy...

--------------------------------------------------------------------------------

How about something like the ado-file below?  I've got only the last release of
Stata (11.2) on the laptop in front of me at the moment, but I believe that it
should work for Stata 12.1, as well.  Put the two directions or senses ("Worse"
and "Improved" in your case) in ascending order in the option for directions,
and do likewise with the ordered degrees or magnitudes ("Slightly", "Moderately"
and "Markedly" in your case) in the option for degrees, paying attention to
case.  If you have a midpoint, put that in the option for zero point.  Take care
with it, because there's no user-input validation; it's pretty lean, but you can
embellish it as you like.

Joseph Coveney

program define engrade
    version 11.2
    syntax varlist(string), DIrections(string) DEgrees(string) ///
        Label(string) [Zero(string)]

    local sign "-"
    foreach direction of local directions {
        local index 0
        foreach degree of local degrees {
            local ++index
            label define `label' `sign'`index' "`degree' `direction'", add
        }
        local sign "+"
    }
    if "`zero'" != "" label define `label' 0 "`zero'", add
    label define `label' .m Missing, add

    tempvar tmpvar0
    quietly foreach var of varlist `varlist' {
        encode `var', generate(`tmpvar0') label(`label') noextend
        replace `tmpvar0' = .m if mi(`var')
        replace `var' = ""
        destring `var', replace
        replace `var' = `tmpvar0'
        label values `var' `label'
        drop `tmpvar0'
    }
end

--- Preliminary Test ---

. input str25 prescores

                     prescores
  1. "Markedly Improved"
  2. "Markedly Worse"
  3. "Moderately Improved"
  4. "Moderately Worse"
  5. "Slightly Improved"
  6. "Slightly Worse"
  7. "Unchanged"
  8. ""
  9. end

. 
. clonevar postscores = prescores
(1 missing value generated)

. 
. engrade *scores, di(Worse Improved) de(Slightly Moderately Markedly) ///
>         l(Improvements) z(Unchanged)

. 
. sort prescores

. list, noobs separator(0) abbreviate(20)

  +-------------------------------------------+
  |           prescores            postscores |
  |-------------------------------------------|
  |      Markedly Worse        Markedly Worse |
  |    Moderately Worse      Moderately Worse |
  |      Slightly Worse        Slightly Worse |
  |           Unchanged             Unchanged |
  |   Slightly Improved     Slightly Improved |
  | Moderately Improved   Moderately Improved |
  |   Markedly Improved     Markedly Improved |
  |             Missing               Missing |
  +-------------------------------------------+

. label list
Improvements:
          -3 Markedly Worse
          -2 Moderately Worse
          -1 Slightly Worse
           0 Unchanged
           1 Slightly Improved
           2 Moderately Improved
           3 Markedly Improved
          .m Missing

. 
. exit

end of do-file

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