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Re: st: Need help with regular expression


From   Michael Stewart <michaelstewartresearch@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Need help with regular expression
Date   Sun, 17 Feb 2013 08:22:38 -0500

Hi Nick and Alison,
One quick question.(sorry, I am a novice to regular expressions)
The two functions di regexm("show us", " us$") & di regexm("show us",
" us&") have different results.
what is the difference between these functions ??
Thank you very much .
Sincerely
Mike

On Sun, Feb 17, 2013 at 5:03 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> Alison's suggestion is surely right. If your condition is not
> restrictive enough, you need to make it more restrictive.
>
> If it is a separate word, it occurs surrounded by spaces or at the
> beginning or end with one space after or before. I tend to build up
> syntax using -display- and little examples.
>
> . di regexm("us marines", "^us ")
> 1
>
> . di regexm("show us", " us$")
> 1
>
> . di regexm("invited us to dinner", " us ")
> 1
>
> You could also use -strpos()-
>
> ... if strpos(var, " us ") | strpos(var, "us ") == 1 | strpos(var, " us") == -3
>
> Note that -regexm()- is a function, not a command. in Stata functions
> and commands are quite separate in definition and documentation.
> -strpos()- is another function. Fixing _function_ firmly in mind as
> the key term leads to consultation of the documentation on functions,
> which as here can suggest alternatives.
>
> There are also solutions with -word()- but they all seem to entail a loop.
>
> Nick
>
> On Sun, Feb 17, 2013 at 8:04 AM, Alison Connor
>
>> I am sure there is a much better way to do this, but until someone who
>> actually knows responds, could you try something like:
>>
>> regexm(var, " us ") | regexm(var, " us&") | regexm(var, "^us ")  ?
>
> On Sun, Feb 17, 2013 at 1:00 PM, Michael Stewart
>
>>> I am trying to use regexm command (regexm(var,"us"))to see if the
>>> values of variable have a particular string "us" like in  "us thyroid"
>>> .Unfortunately , it is picking up "us" from other string values like
>>> "venous".If there a way to formulate command so that it can pick up
>>> only values  where "us" is a separate word and not part of word like
>>> venous.
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-- 
Thank you ,
Yours Sincerely,
Mike.
*
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