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Re: st: Keep/Drop Observations for Top/Bottom X%
From
"Justina Fischer" <[email protected]>
To
[email protected]
Subject
Re: st: Keep/Drop Observations for Top/Bottom X%
Date
Thu, 11 Oct 2012 11:54:58 +0200
Hi Nick,
in principle you might be right.
However, for reasons of practicability it is sometimes recommendable for subset analysis to simply upload the full data and drop a part rather than working with an 'if' restriction throughout all regressions.
HTH
Jusitna
-------- Original-Nachricht --------
> Datum: Thu, 11 Oct 2012 10:46:02 +0100
> Von: Nick Cox <[email protected]>
> An: [email protected]
> Betreff: Re: st: Keep/Drop Observations for Top/Bottom X%
> You need not -keep- or -drop- to do this; in fact -keep- or -drop-
> here is usually a bad idea.
>
> (Furthermore, regressions of this kind are often more problematic than
> they seem, but I'll let others expand on that if they wish.)
>
> For full flexibility here, skip -summarize- and go straight to -_pctile-.
>
> For example,
>
> . sysuse auto
> (1978 Automobile Data)
>
> . _pctile mpg, p(10 90)
>
> . ret li
>
> scalars:
> r(r1) = 14
> r(r2) = 29
>
> So you can follow up with
>
> ... if mpg >= 29
>
> Warnings:
>
> 1. Watch out for ties.
>
> 2. Watch out for missing values at the top end.
>
> ... if mpg >= 29
>
> would include missings on -mpg- (if there were any). -if inrange(mpg,
> 29, .)- excludes the missings.
>
> Nick
>
> On Thu, Oct 11, 2012 at 10:34 AM, Lisa Wang <[email protected]> wrote:
>
> > I am unsure as to how I would go about keeping or dropping the
> > top/bottom X% of observations of a variable. I would like to do this
> > for further analysis on a subset of my data. For instance, I want to
> > do some further regressions for the top 10% of my observations based
> > on 'distance from home' and not the whole data set.
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