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Re: st: Dropping Variables - Simple Question

From   Maarten buis <>
Subject   Re: st: Dropping Variables - Simple Question
Date   Sun, 12 Aug 2007 16:22:32 +0100 (BST)

--- Tiago Pereira asked:
> > Supose I have two variables, X and Y with 50 and 75 observations,
> > respectively. How do I delete the first 25 observations of the
> > variable Y without losing the first 25 observations of the X 
> > variable?

--- Daniel Schneider answered:
> You can't. More importantly, why would you want to do that? Most
> (all?) commands will drop missing values anyway when producing
> results.
There is actually good reason why that is difficult, and that has to do
with the convention that in a dataset the rows represent the
observations. Say we have three observation: one each on individuals
named Maarten, Tiago, and Nick, and consider the following dataset:

id       country
Maarten  . 
Tiago    Brazil
Nick     UK

What would loosing only the first observation of variable country mean?

id       country
Maarten  Brazil 
Tiago    UK
Nick     .


id       country
Maarten  Brazil 
Tiago    Brazil
Nick     UK

or ...

Hope this helps,

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

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

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