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Re: st: RE: marksample


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: marksample
Date   Thu, 11 Sep 2008 14:58:16 +0100 (BST)

--- Ashim Kapoor <ashimkapoor@gmail.com> wrote:
> I am reading mark from the programming manual. I get the idea of
> st_views. I do not understand what the idea behind mark is. Why is
> this variable named in a funny way like __0000 ? Is this 0 / 1 in
> each row depending on some criteria ? What is that criteria?

Often you don't want your program to apply to all observations in your
data, e.g. you want to ignore rows where at least one of the variable
you use in your data contains missing values, or want to allow users to
restrict their analysis to females only. 

-mark- is a convenience command: it collects after -syntax- the
relavant variables and marks out (gives them value 0 on the variable
`touse') observations with missing values on those. It also looks at 
-in- and -if- restrictions.

It is called __000 (though you should never refer to it that way)
because it is a temporary variable: it is removed once your program is
finished. The reason why you should never refer to it that way is that
it could also be called __001 or something else (depending on whether
you have defined other temporary variables before that). You should
refer to it as `touse'.

-- Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room N515

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


      
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