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RE: st: macro problem


From   Nick Cox <n.j.cox@durham.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: macro problem
Date   Mon, 11 Jun 2012 17:29:05 +0100

" " have two roles in Stata; they act as string delimiters (which by default are stripped) and they act as literal characters which you want to preserve as part of a string (in which you often need `" "' as delimiters). 

However, this works

. foreach s in "a b" "b c" "c d" {
  2. di "`s'"
  3. }
a b
b c
c d

so maybe something simpler would also work for you. 

Nick 
n.j.cox@durham.ac.uk 

Jeph Herrin

There is no problem with -strpos-, which never returns missing and which 
is zero exactly when I want it to be. The problem was in creating the 
original macro and then referencing the elements so that they appear in 
-strpos- with the correct number of quotations marks; I was achieving 
either too many or too few of the latter.

The solution (or at least, a solution) is for local -matchlist- needed 
to be enclosed in compound quotes, and then ditto the reference:

    local matchlist `""string 1" "string 2" "string 3" .... "string 55""'

    gen byte match=0
    foreach S of local matchlist {
         replace match = 1 if strpos(strvar,`"`S'"')
    }


The reference in -strpos- looks wrong to me - I would anticipate that 
`S' would include the necessary "'s for -strpos-, but it does not. 
Without the extra quotes on the original local, however, `"`S'"' 
resolves to include too many "'s.

On 6/11/2012 11:58 AM, Richard Goldstein wrote:

> you don't make it clear about what doesn't work
>
> but here is a guess: you are getting match=1 in all cases (or at least
> all where strvar is not missing); remember, however, that strpos=0 if
> "S" is not found; so, in addition to the quotes, etc., I guess you want
> to ensure that strpos is>0 (and maybe<.)

On 6/11/12 11:50 AM, Jeph Herrin wrote:

>> This should be trivial, but for some reason I cannot get it.
>>
>> I have a string variable, and I have a list of string values I need to
>> match against it. There are occasional trailing or leading characters in
>> the variable, so I am using -strpos- to find matches. Thus
>>
>>    local matchlist "string 1" "string 2"  "string 3" .... "string 55"
>>
>>    gen byte match=0
>>    foreach S in `matchlist' {
>>          replace match = 1 if strpos(strvar,`S')
>>    }
>>
>> Now, I know I have got the quotes and macro evaluations wrong, but that
>> is the problem: I've tried this many different ways, and yet cannot seem
>> to find a combination that works. Any thoughts?

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