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st: RE: nested logit model


From   siyama@who.int
To   statalist@hsphsun2.harvard.edu
Subject   st: RE: nested logit model
Date   Tue, 12 Aug 2003 18:51:16 +0200

Hi there,

I will try to suggest the following ,assuming you have a variable called
J=2,3,4,5 and maybe another one Z=1 for the outside choice

sort newid
qui bysort newid: gen choices=3  (if J==4 | J==5)
qui bysort newid: replace choices=2  (if J==2 | J==3)
qui bysort newid: replace  choices=1  (if Z==1)
lab var choices "Options of Choice"

expand 3

sort newid

qui bysort newid: gen temp=_n
qui bysort newid:gen chosen=(temp==choices)
drop choices
rename temp choices
lab var choices "Options of Choice"
lab def choices 1 "Outside" 2 "S1" 3 "S2"
lab val choices choices


nlogitgen type=choices(Outside:1, Other: 2 3)
nlogittree choices type

/***	If you have  explanatory variables, say educ and sex (as binaries)
then you can hold the "Outside" option as the baseline**/

for var educ sex: for Y in new S1: gen XY=X*(choices==2)
for var educ sex: for Y in new S2: gen XY=X*(choices==3)

/***	Here you need something to hold the content of the constant, try **/

gen consC=(type==2)
xi:nlogit chosen (choices = educS1 sexS1 educS2 sexS2) (type = consC),
group(newid)



I hope you find this helpful. Perhaps you can also check the VALUABLE
instructions posted by Weihua Guan (wguan@stata.com) at
http://www.stata.com/statalist/archive/2002-10/msg00187.html



Amani




-----Original Message-----
From: Wei Tan [mailto:tanwei@hotmail.com]
Sent: Tuesday, 12 August 2003 17:49
To: statalist@hsphsun2.harvard.edu
Subject: st: nested logit model


Hi,

I need to estimate a nested logit model including outside alternatives.

In my model, I have four choices, j=2,...5 and an outside alternatives j=1.

I group the four choices to two group S1={3,2} and S2={5,4}

at the upper layer of nest, I have choice 1, S1 and S2.

I used the following command

nlogit chosen (choice=price) /*
		*/ (type2= x), group(newid)  ivc(choicezero=1)

the nest structure shows

type2                  choice
choicezero            1
S1                       2
                          3
S2                       4
                          5

the program shows an error message

choicezero not found
r(198)

I guess that my problem is that I did not specify the model correctly. I 
wonder if someone could help me how to specify the correct model.

wei

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