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

To |
statalist@hsphsun2.harvard.edu |

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

Date |
Fri, 1 Feb 2013 08:44:44 +0000 |

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/

**Follow-Ups**:**Re: st: bug in -xtile-***From:*"Dr. Yu Chen" <profyuchen@gmail.com>

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