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From |
Grace Jessie <gracejessie@hotmail.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: How does Stata calculate percentiles? |

Date |
Mon, 25 Oct 2010 05:05:04 +0000 |

Phil,Nick, thank you a lot for replies. -centile- works well. However, does centile(33) equal to centile 100/3 I want to get? Nick, thank you for reminder.I keep the variable and just do some statistics for the variable, so no loss of information. Grace ---------------------------------------- > From: n.j.cox@durham.ac.uk > To: statalist@hsphsun2.harvard.edu > Date: Sun, 24 Oct 2010 17:42:23 +0100 > Subject: RE: st: How does Stata calculate percentiles? > > Phil gave a good answer. However, once you have the -centile- result in memory, > > local cutpoint=r(c_1) > recode price (min/`cutpoint'=0) (`cutpoint'/max=1), gen(pricecat) > > can be replaced by one line > > gen pricecat = (price >= r(c_1)) if !missing(price) > > which yields 0, 1 and numeric missing as appropriate. > > On the other hand, why do you want to throw away information like this? > > Nick > n.j.cox@durham.ac.uk > > Phil Clayton > > One way to do it would be to obtain the centile using the -centile- command, then -recode- the variable to create the indicator variable. > > Example: > sysuse auto > centile price, centile(33) > local cutpoint=r(c_1) > recode price (min/`cutpoint'=0) (`cutpoint'/max=1), gen(pricecat) > > If you wanted the indicator variable to be 1 if the variable is >= the cutpoint (as opposed to >), swap the two recoding rules (once one rule is matched, the subsequent rules are ignored). > > See the manual for -centile- to see how it's calculated. It's pretty standard. With regards to "su varname, d", see -help summarize- and the manual for -summarize- > > On 24/10/2010, at 3:27 PM, Grace Jessie wrote: > > > I want to generate a new variable equaling 1 if the other variable is greater than its 100/3 percentile and 0 otherwise.How to get the 100/3th percentile of a variable? > > And how does Stata calculate percentiles if the number of observations is odd or even? > > Additionally, what does the output "smallest and largest" mean after "su varname,d"? > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/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/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: How does Stata calculate percentiles?***From:*Nick Cox <n.j.cox@durham.ac.uk>

**Re: st: How does Stata calculate percentiles?***From:*Phil Clayton <philclayton@internode.on.net>

**References**:**st: How does Stata calculate percentiles?***From:*Grace Jessie <gracejessie@hotmail.com>

**Re: st: How does Stata calculate percentiles?***From:*Phil Clayton <philclayton@internode.on.net>

**RE: st: How does Stata calculate percentiles?***From:*Nick Cox <n.j.cox@durham.ac.uk>

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