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RE: st: RE: Using results from correlation matrices to pinpoint variables


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Using results from correlation matrices to pinpoint variables
Date   Sun, 19 Jun 2005 17:13:57 +0100

OK. Suppose you -sort- a numeric variable: 

sort myvar 

Then, if at least one value of -myvar- 
is missing, it follows that the last value 
will be missing, as any missing values have been -sort-ed to 
that end. So that you could do this 

sort myvar 
if missing(myvar[_N]) drop myvar 

to get rid of a variable with any missing values. 

Also, if a numeric variable were all missing, 
then 

sort myvar 
if missing(myvar[1]) & missing(myvar[_N]) drop myvar 

would drop such a variable. 

On the whole, however, 

if <condition> <command> 

doesn't much feature in decisions on whole 
variables. 

-dropmiss- itself just uses -count- for this problem and does
nothing to the -sort- order, even internally. 

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

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Alejandro
> Delafuente
> Sent: 19 June 2005 16:38
> To: statalist@hsphsun2.harvard.edu
> Subject: RE: st: RE: Using results from correlation matrices 
> to pinpoint
> variables
> 
> 
> okey, in that case the solution was: using the command 
> dropmiss with the 
> option any, so that all variables with missings would be 
> dropped out. As for 
> the if distinction between qualifier and command, that was 
> already clear to 
> me, or at least that is what I thought.
> Alex
> In message 
> <031173627889364697C50B3B266CBB8A101BC6@GEOGMAIL.geog.ad.dur.ac.uk> 
> statalist@hsphsun2.harvard.edu writes:
> > A thread is best closed by saying what the 
> > solution was, not that you found a solution.... 
> > 
> > Nick 
> > n.j.cox@durham.ac.uk 
> > 
> > Alejandro Delafuente
> >  
> > > many thanks Nick. I sorted out the problem.
> > > 
> > > In message 
> > > 
> <031173627889364697C50B3B266CBB8A101BAF@GEOGMAIL.geog.ad.dur.ac.uk> 
> > > statalist@hsphsun2.harvard.edu writes:
> > > > My guess is that what you are getting what you 
> > > > ask for, but that it is not what you want. 
> > > > 
> > > > The difference between 
> > > > 
> > > > 	if <condition> <command> 
> > > > 
> > > > and 
> > > > 
> > > > 	<command> if <condition> 
> > > > 
> > > > is profound. For one documentation, see
> > > > http://www.stata.com/support/faqs/lang/ifqualifier.html
> > > > 
> > > > I am not clear what you want precisely. If you 
> > > > want to drop a variable if and only if all observations
> > > > are missing, then 
> > > > 
> > > > . search dropmiss 
> > > > 
> > > > for a convenience command. 
> > > > 
> > > > Nick 
> > > > n.j.cox@durham.ac.uk 
> > > > 
> > > > Alejandro Delafuente
> > > > > 
> > > > > Dear Nick, thanks for your advice. With some little 
> > > > > adjustments it worked out! 
> > > > > Also, taking advantage of your generosity let me ask you a 
> > > > > quick question: am 
> > > > > trying to drop some monthly variables in a time sequence 
> > > > > (from january 1961 to 
> > > > > dec 2001) with missings in them. My code looks as follows:
> > > > > foreach var of varlist jan* feb* ... dec* {
> > > > > 	if `var' ==. {
> > > > > 	drop `var' 
> > > > > 	}
> > > > > }
> > > > > But for some reason it is not working. Can you tell why?
> > > > > As always, many thanks.
> > 
> > *
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> > *   http://www.ats.ucla.edu/stat/stata/
> > 
> 
> -- 
> Alejandro de la Fuente
> QEH/Department of International Development
> Oxford University
> *
> *   For searches and help try:
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> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
> 

*
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