RE: st: RE: two STATA questions

["Ni Frank" <frankflying03@hotmail.com>]

Got it. You are right. I was thinking about the second quetion which keeps 
those observations at least one of variables is zero.

Thanks again!

Frank


> From: "Nick Cox" <n.j.cox@durham.ac.uk>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: <statalist@hsphsun2.harvard.edu>
> Subject: RE: st: RE: two STATA questions
> Date: Tue, 27 Feb 2007 09:49:33 -0000
>
> Wrong. -drop if count- is equivalent to -drop if count != 0- which in this
> case would only arise -if count > 0-.
>
> Besides, you asked for -drop-ping or -keep-ing if and only if at least
> one variable were zero. The variable -count- is a count of the number
> of variables in which values are zero in each observation. So,
>
> drop if count == 0
>
> would -drop- only those observations in which no values were zero.
>
> There is more on constructs like -if count- in
>
> FAQ     . . . . . . . . . . . . . . . . . . . . . . .  True and false in 
Stata
>         2/03    What is true and false in Stata?
>         http://www.stata.com/support/faqs/data/trueorfalse.html
>
> Nick
> n.j.cox@durham.ac.uk
>
> Ni Frank
>
> >    Oh,I see. By the way, the "drop if count" should be "drop
> > if count==0",
> > right? I have tried your method. It works. Thanks very much!
>
> Nick Cox
>
> > > > 1) There are 50 varialbes, w05100, w05200,....,w10000. We
> > > > want to DROP
> > > > those obversations for which at least one of the above
> > > > variables takes
> > > > value of 0.  When I use "drop if w*==0, it said "W* invalid name".
> > > > Does anybody know what's wrong?
> > >
> > >That's illegal. You can't put a wildcard there after -if-.
> > An expression
> > >can go there, but a wildcard doesn't qualify as an expression.
> > >
> > >Here is one way to do it.
> > >
> > >gen byte count = 0
> > >
> > >qui forval i = 5100(100)10000 {
> > >	replace count = count + (w0`v' == 0)
> > >}
> > >
> > >drop if count
> > >
> > > > 2)  Now, if we want to KEEP those obersvations for which
> > at least one
> > > > of the variables w05100, w05200, ....,w09900 takes value
> > of 0. How to
> > > > do that?
> > >
> > >It's the same story, except for -keep- instead of -drop-.
>
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