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RE: st: How to use r(p)


From   "David Harrison" <david.harrison@icnarc.org>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: How to use r(p)
Date   Mon, 12 Sep 2005 11:07:18 +0100

Almost... You will need to store the percentiles in local macros (as the return values r() get overwritten by regress):

_pctile d, p(33 66)
local p33=r(r1)
local p66=r(r2)
reg y a b c if d<=`p33'
reg y a b c if d>`p33' & d<`p66'
reg y a b c if d>=`p66'

Alternatively, you may find it easier by creating a new categorical variable for the 3 groups. e.g.

xtile byte pc=d, n(3)
bysort pc: reg y a b c

Hope this helps

David

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of FUKUGAWA, N.
Sent: 12 September 2005 10:03
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: How to use r(p)


Dear all,
What if we want to run 3 regression models according to the classification of 
variable "d"?

centile d, centile(33)
centile d, centile(66)
reg y a b c if d<=r(c_1)
reg y a b c if d>r(c_1)&d<r(c_2)
reg y a b c if d>=r(c_2)

Thank you in advance.
--
FUKUGAWA Nobuya, Ph.D.
nfukugawa@gmail.com

Jean-Benoit Hardouin wrote:
> You can try
> . centile d, centile(33)
> . reg y a b c if d>r(c_1)
> Best,
> Jean-Benoit Hardouin
> 
> FUKUGAWA, N. a écrit :
> 
>> Dear all,
>> Suppose we want to limit observations where one variable records a 
>> larger value
>> than its top quartile, we can write as follows.
>>
>> sum d,detail
>> reg y a b c if d>r(p75)
>>
>> However, this program allows only fixed thresholds such as 1, 10, and 
>> 75 percent.
>> How can I use other thresholds such as r(p33) in the program?
>> Or, is there any program to do the same?
>> Thanks in advance.
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