Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: Dropping Variables - Simple Question


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
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     .

or:

id       country
Maarten  Brazil 
Tiago    Brazil
Nick     UK

or ...

Hope this helps,
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 Z434

+31 20 5986715

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


      ___________________________________________________________
Yahoo! Answers - Got a question? Someone out there knows the answer. Try it
now.
http://uk.answers.yahoo.com/ 
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index