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Re: st: RE: question on nested logit


From   "Data Analytics Corp." <walt@dataanalyticscorp.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: question on nested logit
Date   Mon, 03 Sep 2012 16:28:56 -0400

Sorry.  I forgot to include the signature;

Walt

________________________

Walter R. Paczkowski, Ph.D.
Data Analytics Corp.
44 Hamilton Lane
Plainsboro, NJ 08536
________________________
(V) 609-936-8999
(F) 609-936-3733
walt@dataanalyticscorp.com
www.dataanalyticscorp.com


_____________________________________________________

On 9/3/2012 2:57 PM, Lachenbruch, Peter wrote:
do you have a name other than Walt?  See FAQ about submitting anonymously
Peter A. Lachenbruch,
Professor (retired)
________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] On Behalf Of Data Analytics Corp. [walt@dataanalyticscorp.com]
Sent: Monday, September 03, 2012 10:09 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: question on nested logit

Hi,

I'm experimenting with the nested logit setup for a coffee demand study
I want to do.  Here's a sample of the data:

+-----------------------------------------------------------------------------------------------------+
       | id   choice      form       flavor   size   price brandc~e
brand      FLAVORX     FORMX    SIZEX |
|-----------------------------------------------------------------------------------------------------|
    1. |  1        0         BagGr    UnLgt     16    2.25 4 Folgers
UNFLAVORED    BAGGED   MEDIUM |
    2. |  1        0         BagWh    UnMed     20       3 7 SBUX
UNFLAVORED    BAGGED    LARGE |
    3. |  1        0         Can         UnDK     18 2.75          6
Classico   UNFLAVORED    CANNED   MEDIUM |
    4. |  1        0         Pods        Hazel     10     3.1 1
DD     FLAVORED      PODS    SMALL |
    5. |  1        0       InstCan      Van     24    1.75 8 Store
FLAVORED   INSTANT    LARGE |
|-----------------------------------------------------------------------------------------------------|
    6. |  1        0    InstSt    Other      4     2.5 5 Peet
FLAVORED   INSTANT    SMALL |
    7. |  1        0       Mix    UnLgt     12    3.25          3
Maxwell   UNFLAVORED     MIXES   MEDIUM |
    8. |  1        1       Liq    UnMed      8     1.5 2 Godiva
UNFLAVORED    LIQUID    SMALL |
    9. |  2        0     BagGr     UnDK     16    2.25          4
Folgers   UNFLAVORED    BAGGED   MEDIUM |
   10. |  2        0     BagWh    Hazel     20       3 7 SBUX
FLAVORED    BAGGED    LARGE |
+-----------------------------------------------------------------------------------------------------+

The data are read from a text file using a Do File which also creates
the nested logit tree:

#delimit ;
insheet using "C:\Temp\coffee.txt", clear;
label drop _all;
nlogitgen FLAVORX = flavor(UNFLAVORED: UnLgt | UnMed | UnDK, FLAVORED:
Hazel | Van | Other);
nlogitgen FORMX = form(BAGGED: BagGr | BagWh, CANNED: Can, INSTANT:
InstCan | InstSt, MIXES: Mix, LIQUID: Liq, PODS: Pods);
nlogitgen SIZEX = size(SMALL: 4 | 8 | 10, MEDIUM: 12 | 16 | 18, LARGE:
20 | 24);
nlogittree brand FORMX FLAVORX SIZEX, choice(choice);

Stata returns an error message:

. nlogittree brand FORMX FLAVORX SIZEX, choice(choice);
invalid tree structure; input bottom level first
r(198);

Why?  No matter how I arrange FORMX, FLAVORX, and SIZEX, I get an
error.  I want brand to be at the bottom of the tree and it's specified
first, as it should be.  Everything seems correct.  But obviously I'm
missing something.  Any help?

I'm using Stata 11 on a Windows PC.

Thanks,

Walt
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