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st: RE: about centile and r(c_#)


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: about centile and r(c_#)
Date   Wed, 7 Apr 2010 18:35:55 +0100

-centile- numbers its results 1, 2, etc. not in terms of the percents
you specified. Thus 

. return list 

will show that after your command r(c_1) and r(c_2) are specified.
r(c_30) would be specified only if you had asked for 30 or more
percentiles. 

I guess this numbering convention is to avoid precision problems if
anyone asks for percentiles that do not correspond to integer percents. 

Nick 
n.j.cox@durham.ac.uk 

G. Dai

I'm lit bit confused by centile. for example
************************
.clear
.sysuse auto

. centile price, c(30   60)

                                                       -- Binom. Interp.
--
    Variable |     Obs  Percentile      Centile        [95% Conf.
Interval]
-------------+----------------------------------------------------------
---
       price |      74         30        4424.5        4110.565
4679.134
             |                 60          5705        4912.708
6232.007

*************************

then I want to know the values of centiles, say

*****************************
. di r(c_30)
*****************************
I get missing values.

while

**************************
. di $S_7
4424.5
**********************

so, why r(c_30) doesn't work and why $S_7 works?


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