Re: st: Dropping not valid emails

[Phil Schumm <pschumm@uchicago.edu>]

On Feb 19, 2008, at 5:10 AM, Alexander.Severinsen@telenor.com wrote:
> I have a variable that contains e-mail adresses. I would like to  
> find a way to drop observations that does not contain valid email  
> adresses.  There should be a condition that the string contains one  
> '@', the exsistence of period, and two or three characters  
> following the period, and no empty spaces.

This is best handled with a regular expression (i.e., with the -regexm 
()- function).  For example, the following regular expression will  
match most valid email addresses:

    ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z][a-zA-Z][a-zA-Z]?[a- 
zA-Z]?$

Unfortunately, Stata's lack of support for curly braces (used to  
indicate bounds) means that you cannot use the following, shorter  
expression:

    ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$

which is essentially the same as the one above.  But the first one  
will work fine with -regexm()-.


-- Phil

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