[Limdep Nlogit List] Heuristics & latent classes using Maximize in nlogit 5. How can I take into account the quasi-panel structure of experiment?

Thu Jun 22 19:31:34 AEST 2017

Dear Melanie, 

Thank you for the remark. In fact, it is an unlabeled experiment with a
status quo option (SQ). The first alternative is the SQ, and so I coded it
so that only that SQ equation get an intercept (to estimate the value of the
SQ as compared to adopt one of the two alternatives).  In any case this does
not prevent the model to run. 

In any case, thank you for your careful observation.

Damien 

-----Message d'origine-----
De : limdep-bounces at limdep.itls.usyd.edu.au
[mailto:limdep-bounces at limdep.itls.usyd.edu.au] De la part de Melanie
Velarde
Envoyé : Thursday, June 22, 2017 1:36 PM
À : Limdep and Nlogit Mailing List
Objet : Re: [Limdep Nlogit List] Heuristics & latent classes using Maximize
in nlogit 5. How can I take into account the quasi-panel structure of
experiment?

Dear Damien,

I cannot answer your question, sorry...
But I noticed that you're missing a constant in your model specification,
which I find unusual...
Just wanted to point that out, in case that didn't happen on purpose.

Best regards,

Melanie Velarde

-----Ursprüngliche Nachricht-----
Von: limdep-bounces at limdep.itls.usyd.edu.au
[mailto:limdep-bounces at limdep.itls.usyd.edu.au] Im Auftrag von Damien
Jourdain
Gesendet: Mittwoch, 21. Juni 2017 06:22
An: limdep at limdep.itls.usyd.edu.au
Betreff: [Limdep Nlogit List] Heuristics & latent classes using Maximize in
nlogit 5. How can I take into account the quasi-panel structure of
experiment?

Dear List members,

Sorry for the long message, but this is to describe the different steps
before reaching my problem!

We are analyzing a choice experiment using Nlogit5. 
? MNL Model
NLOGIT; 
    ; Choices = 1,2,3
    ; Lhs = Choice
    ; Rhs = SQ , BEN10, LAB10, CAS10, RISK10, ST, FERTHI, FERTLO $

During the interviews, we had noticed that many respondents tended to
eliminate the alternative when FERTLO = 1 and FERTHI = 0  (in fact FERT is a
nominal variable that we effect coded into FERTLO and FERTHI), we would like
to test whether the heuristic is present in the population.  I have looked
at the Hensher et al. 2015, Applied choice analysis book and came out with
the following procedures. (but I am using Nlogit 5 so far)

First I checked that I could use Maximize to reproduce the simple MNL.

Sample; All$
create; ch0 = Choice; ch1 = Choice[+1]; ch2 = Choice[+2]$ create; ben0 =
ben10; ben1 = ben10[+1]; ben2 = ben10[+2]$ create; lab0 = lab10; lab1 =
lab10[+1]; lab2 = lab10[+2]$ create; cas0 = cas10; cas1 = cas10[+1]; cas2 =
cas10[+2]$
create; sto0 = st;    sto1 = st[+1];    sto2 = st[+2]$
create; fhi0 = ferthi; fhi1 = ferthi[+1]; fhi2 = ferthi[+2]$ create; flo0 =
fertlo; flo1 = fertlo[+1]; flo2 = fertlo[+2]$ create; J = Trn(-3, 0)$
reject; J > 1$

Namelist; 
	x0 =  ben0, lab0, cas0, sto0, fhi0, flo0; 
	x1 =  ben1, lab1, cas1, sto1, fhi1, flo1; 
	x2 =  ben2, lab2, cas2, sto2, fhi2, flo2 $ Calc; ks = Col(x0)$
Matrix; cs = init(ks,1,0.1) $

Maximize
 ; labels = interc, ks_bs
 ; start  = 0.1, cs
 ; maxit = 30
 ; Fcn =
ut0 = interc+ bs1'x0  |  v0 = exp(ut0) |
ut1 = bs1'x1  |   v1 = exp(ut1) |
ut2 = bs1'x2 |v2 = exp(ut2) |
IV =  v0+ v1 + v2 |
P = ( ch0*v0 + ch1*v1 + ch2*v2)/ IV |
log(P) ;
Output=1$

It gave the same results. 

Then I produced an Indicator variable  (being equal to zero when the fertlo
is present. It helps me modify the utility functions so that the utility of
one alternative is equal to zero when the attribute is present.

create; I1=1$
create; I2=1$
create; if(flo1=1 & fhi1= 0)I1=0$
create; if(flo2=1 & fhi2= 0)I2=0$

Maximize
 ; labels = intercep, ks_bs
 ; start  = 0.1, cs
? ; maxit = 30
 ; Fcn =
ut0 = intercep+ bs1'x0  |  v0 = exp(ut0) |
ut1 = I1 * (bs1'x1)  |   ? the utility is becoming null when the fertlo
indicator is present in the alternative
v1 = exp(ut1) |
ut2 = I2*(bs1'x2) | v2 = exp(ut2) |
IV =  v0+ v1 + v2 | P = ( ch0*v0 + ch1*v1 + ch2*v2)/ IV |
log(P) ;
Output=1$

Finally I am trying to develop a latent class analysis so that I can
identify whether the two types of heuristics are present in the sample.
? Latent class analysis

Calc; ks2 = Col(x0)$
Matrix; cs2 = init(ks2,1,0.1) $

Maximize
 ; labels = inter, ks_ba, inter2, ks2_bb, gamma  ; start  = 0.1, cs, 0.1,
cs2, 0.1  ; maxit  = 30  ; Fcn =
ut0c1 = inter+ ba1'x0  |  v0c1 = exp(ut0c1) |
ut1c1 = ba1'x1  |v1c1 = exp(ut1c1) |
ut2c1 = ba1'x2 |v2c1 = exp(ut2c1) |
IVc1 =  v0c1+ v1c1 + v2c1 |
Pc1 = ( ch0*v0c1 + ch1*v1c1 + ch2*v2c1)/ IVc1 |

ut0c2 = inter2+ bb1'x0  | v0c2 = exp(ut0c2) |
ut1c2 = I1 * (bb1'x1)  | v1c2 = exp(ut1c2) |
ut2c2 = I2*(bb1'x2) | v2c2 = exp(ut2c2) |
IVc2 =  v0c2+ v1c2 + v2c2 |
Pc2 = ( ch0*v0c2 + ch1*v1c2 + ch2*v2c2)/ IVc2 |

Pprob = 1 / (1+exp(gamma))|
P = Pprob * Pc1 + (1-Pprob) * Pc2 |
log(P) ;
Output=1$

While the model is running ok, I realize that I am not taking into account
the fact that respondents are actually answering 6 choice sets
(quasi-panel?), but I cannot find a meaningful way to write that using
Maximize ?  Anybody already faced this kind of issue?  

Best, 

Damien 

Dr. Damien Jourdain
Agricultural and Natural Resources Economist Visiting Assistant Professor
Asian Institute of Technology / CIRAD G-EAU Natural Resource Management /
Water Engineering and Management

mail: djourdain at ait.asia

web GEAU : www.g-eau.net
web NRM : www.nrm.ait.asia

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