Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

RE: Missing values [was: RE: st: simple question]


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: Missing values [was: RE: st: simple question]
Date   Sun, 6 Jun 2004 18:30:24 +0100

For consistency with what? 

Each program has its own design style. 
The SAS/Stata difference on missing
values as very low/very high hinges
on the Stata preference for _not_ seeing 
a wadge of missings first after 

. sort myvar 
. list myvar 

Also, each program must make its own decisions 
about missing data, in which a Murphy-type 
Law applies: 
Whatever you do is wrong for some circumstances. 

By and large, Stata follows the Unix 
tradition of assuming smart users and giving 
minimal, or least restricted, output. 

So, with -graph- or -regress- on variables with 
some missing values they can't be used -- 
and there is no message reminding you of 
that. 

With -tabulate- the situation is not 
so clear-cut. 

However, with say  

. tabulate row col, chi2 

I personally would not want a default 
in which missing categories became 
extra rows and columns. To put 
it another way, the difficulty 
arises because -tabulate- has both 
statistical and data management roles. 

It seems to me on this Stata is, as 
close as possible, being 
consistent with its own general 
conventions: you can't graph missings, 
you can't do statistics with missings, 
but you can do data management with 
missings.  

Nick 
n.j.cox@durham.ac.uk 

Joseph Coveney
> 
> Whoops!  Apparently not.  (SAS codes missing values as the 
> smallest possible 
> value, while Stata codes them as the largest.)
> 
> Perhaps, for consistency, Stata ought to include missing 
> categories in  
> -tabulate- by default . . .

*
*   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