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Re: st: replacing zero length strings with missing values


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: replacing zero length strings with missing values
Date   Tue, 4 Sep 2012 13:20:43 +0100

Should be

A string value is missing if and only if it is empty. (That is, the
function -missing()- returns 1 for true with string
arguments if and only if that string argument is empty.)

Nick

On Tue, Sep 4, 2012 at 1:15 PM, Nick Cox <njcoxstata@gmail.com> wrote:
> You tried to replace empty strings with numeric missing . --  but, as
> you report here, that is a type mismatch.
>
> There is nothing to do here: empty strings and missing strings are one
> and the same in Stata. Consider
>
> . di missing("")
> 1
>
> . di missing(" ")
> 0
>
> . di missing("frog")
> 0
>
> A string value is missing if and only if it is empty. (That is, the
> function -missing()- returns 1 for true if and only with string
> arguments if and only if that string argument is empty.)
>
> It is possible to replace "" with "." if you wish to show empty
> strings explicitly, but that's all in the eye of the beholder: Stata
> does not regard "." as denoting string missing: it's just a stop or
> period character.
>
> Nick
>
> On Tue, Sep 4, 2012 at 12:54 PM,  <Robert.Shaw@dh.gsi.gov.uk> wrote:
>
>> I have a large dataset in stata and one of the variables has a lot a
>> observations that should be missing values but are instead zero length
>> strings (ie. =="")
>>
>> I've tried
>>
>> foreach x of varlist myvariable {
>> replace `x' = . if(`x' =="")
>> }
>>
>> but this gives a type mismatch.
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