Notice: On March 31, it was **announced** that Statalist is moving from an email list to a **forum**. The old list will shut down on April 23, and its replacement, **statalist.org** is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Keep/Drop Observations for Top/Bottom X% |

Date |
Thu, 11 Oct 2012 11:11:34 +0100 |

I don't fully understand the question. If you want to slice at a percentile (quantile), you have to calculate a percentile somehow. You could always write a program that does some combination of calculating the percentile _and_ some analysis via a single call and if you were doing this many, many times that would be a good idea. I don't think such a program exists already canned. Nick On Thu, Oct 11, 2012 at 10:59 AM, Lisa Wang <lhwang0925@gmail.com> wrote: > Thank you everyone for your suggestions. But I was wondering is there > a way to code it up such that I don't need to do -summa- or -_pctile- > and then look at the output to determine what the cutoff values will > be for the top/bottom X% before I do the next step? > > Thank you again, > Lisa > > > On Thu, Oct 11, 2012 at 8:54 PM, Justina Fischer <JAVFischer@gmx.de> wrote: >> 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 <njcoxstata@gmail.com> >>> An: statalist@hsphsun2.harvard.edu >>> 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 <lhwang0925@gmail.com> 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. >>> * >>> * For searches and help try: >>> * http://www.stata.com/help.cgi?search >>> * http://www.stata.com/support/faqs/resources/statalist-faq/ >>> * http://www.ats.ucla.edu/stat/stata/ >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Keep/Drop Observations for Top/Bottom X%***From:*Lisa Wang <lhwang0925@gmail.com>

**Re: st: Keep/Drop Observations for Top/Bottom X%***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: Keep/Drop Observations for Top/Bottom X%***From:*"Justina Fischer" <JAVFischer@gmx.de>

**Re: st: Keep/Drop Observations for Top/Bottom X%***From:*Lisa Wang <lhwang0925@gmail.com>

- Prev by Date:
**Re: st: Keep/Drop Observations for Top/Bottom X%** - Next by Date:
**Re: st: Keep/Drop Observations for Top/Bottom X%** - Previous by thread:
**Re: st: Keep/Drop Observations for Top/Bottom X%** - Next by thread:
**Re: st: Keep/Drop Observations for Top/Bottom X%** - Index(es):