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Re: st: if vx==1 (replace v1=1 if v1 is missing, otherwise replace v2=1 ... : how do i do this?


From   "paul o'brien" <paul.obrien@afe2.org.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: if vx==1 (replace v1=1 if v1 is missing, otherwise replace v2=1 ... : how do i do this?
Date   Thu, 26 May 2011 12:44:08 +0100

thanks for this Nick.

the thing is, i want second and third replacements to be conditional
on the first and second, so the second replacement occurs only if the
v1 is not missing and the third if both v1 and v2 are not missing. so,
only one change required - either at v1, v2 or v3.

Paul

On 25/05/2011, Nick Cox <njcoxstata@gmail.com> wrote:
> I am not sure that you mean what you say by "otherwise". What is
> definite is that
>
> if vx == 1
>
> as a command will be interpreted as
>
> if vx[1] == 1
>
> which is unlikely to be what you want. See
>
> FAQ     . . . . . . . . . . . . . . . . . . . . .  if command vs. if
> qualifier
>         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  J.
> Wernow
>         6/00    I have an if command in my program that only seems
>                 to evaluate the first observation, what's going on?
>                 http://www.stata.com/support/faqs/lang/ifqualifier.html
>
> for detailed explanation.
>
> I am assuming that -vx- is not a scalar, but a variable.
>
> It sounds as if you want statements like these:
>
> replace v1 = 1 if missing(v1) & vx == 1
>
> If you really want the "otherwise", you will need something like this
>
> gen ismissv1 = missing(v1)
> gen ismissv2 = missing(v2)
> replace v1 = 1 if missing(v1) & vx == 1
> replace v2 = 1 if missing(v2) & vx == 1 & !ismissv1
> replace v3 = 1 if missing(v3) & vx == 1 & !ismissv1 & !ismissv2
>
> Somehow I guess that you are after something more like this
>
> replace v1 = 1 if missing(v1) & vx == 1
> replace v2 = 1 if missing(v2) & vx == 1
> replace v3 = 1 if missing(v3) & vx == 1
>
> although you don't mention the missing(v3).
>
> Nick
>
> On Wed, May 25, 2011 at 7:57 PM, Paul O'Brien <paul.obrien@afe2.org.uk>
> wrote:
>> i cannot think how to do this in Stata:
>>
>> if vx==1 (replace v1=1 if v1 is missing, otherwise replace v2=1 if v2 is
>> missing, otherwise replace v3=1).
>>
>> thanks for any help you can give.
>>
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