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From |
"Dr. Yu Chen" <profyuchen@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: bug in -xtile- |

Date |
Fri, 1 Feb 2013 09:02:00 -0600 |

Thank you Nick for the confirmation. I hope this issue will be corrected in Stata 13. On Fri, Feb 1, 2013 at 2:44 AM, Nick Cox <njcoxstata@gmail.com> wrote: > > Now I agree with you. The code for -xtile- includes the test > > if `nquanti' > _N + 1 { > di in red "nquantiles() must be less than or " /* > */ "equal to number of observations plus one" > exit 198 > } > > but a better test would be something like > > marksample touse > qui count if `touse' > > if `nquanti' > r(N) + 1 { > > The total number of observations _N is not the right number to check > against. > > Nick > > On Fri, Feb 1, 2013 at 3:21 AM, Dr. Yu Chen <profyuchen@gmail.com> wrote: > > > Nick, if this is -xtile- point of view, then it will not work if I > > delete observations whose value<5000. See my code below. > > In other words, in the first example I added an if condition, and in > > the second example, I deleted those observations. Why is the result > > different? I think this is an inconsistency in -xtile-. > > > > sysuse auto,clear > > keep in 1/10 > > drop if price<5000 > > xtile decile=price , nq(10) > > > On Thu, Jan 31, 2013 at 8:08 PM, Nick Cox <njcoxstata@gmail.com> wrote: > >> In your example 6 values qualify as < 5000. -xtile- classifies into 10 > >> classes as best it can > >> > >> (Here -groups- is from SSC.) > >> > >> . groups price decile, sep(0) > >> > >> +----------------------------------+ > >> | price decile Freq. Percent | > >> |----------------------------------| > >> | 3,799 1 1 16.67 | > >> | 4,082 2 1 16.67 | > >> | 4,099 4 1 16.67 | > >> | 4,453 6 1 16.67 | > >> | 4,749 7 1 16.67 | > >> | 4,816 9 1 16.67 | > >> +----------------------------------+ > >> > >> You seem to be saying that they should not be classified if there are > >> less than 10. That's a point of view, but it is not -xtile-'s point of > >> view. > >> > >> The values are of the new variable are not equally spaced integers, > >> but they could not be given the request. > >> > >> Nick > >> > >> On Fri, Feb 1, 2013 at 1:45 AM, Dr. Yu Chen <profyuchen@gmail.com> > >> wrote: > >>> I think there is a bug in -xtile-. I ran the code below, and I still > >>> got deciles, but they are incomplete. I would expect missing values > >>> because there are not enough observations. > >>> I use Stata 12. > >>> > >>> sysuse auto,clear > >>> keep in 1/10 > >>> xtile decile=price if price<5000, nq(10) > * > * 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**:**Re: st: bug in -xtile-***From:*Nick Cox <njcoxstata@gmail.com>

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