[Limdep Nlogit List] Simulating unconditional WTP
Damien Jourdain
djourdain at ait.asia
Wed Apr 4 00:56:50 AEST 2018
Dear All,
I ran the following RPL-EC model. It gives me reasonable results.
? ML-EC Model
Sample; ALL$
Calc; Ran(12345)$
RPLOGIT
; Choices = 1,2,3
; Lhs = CHOICE, CSET, ALT
; Model:
U(1) = A1 + BE*BENEF + LA*LAB + CA*CASH +RI*RISK + FEL*FERTLO +FEH*
FERTHI /
U(2,3) = BE*BENEF + LA*LAB + CA*CASH +RI*RISK + FEL*FERTLO +FEH*
FERTHI
; Fcn = BE(l), LA(n), CA(n), RI(n), FEH(n)
; Pds = 6
; Pts = 20
; Shuffled
; Correlation
; WTP = LA/BE, CA/BE, RI/BE, FEH/BE
; ECM = (2,3)
; Parameters
; Maxit = 300$
I have obtained the conditional WTP (using the WTP command) but in fact I
would like to manipulate simulated un-conditional WTPs. As the coefficients
are correlated, I understand that I have to use the Cholesky decomposition
(provided in the model output) to be able to draw correlated random
coefficients. I have two set of questions:
First, can I use the WALD command to develop these simulations (I know this
can be done with an MNL model, but I do not see any simple manner to use the
B and VARB matrices obtained from the model for a RPL model.
Second, as I assumed that I could not use WALD, I developed the following
commands for simulating the first three random coefficients:
SAMPLE; 1-1000$
create
; rna1 = rnn(0,1)
; rna2 = rnn(0,1)
; rna3 = rnn(0,1)
; rna4 = rnn(0,1)
; rna5 = rnn(0,1)
; rna6 = rnn(0,1)
; MUBEN = B(1) + B(8) * RNA1
; MULAB = B(2) + B(13) * RNA2 + B(9) * RNA3
; MUCAS = B(3) + B(14) * RNA4 + B(15) * RNA5 + B(10) * RNA6
$
(the coefficients are correct and correspond to the Cholesky matrix
coefficients )
When checking the simulated coefficients, I can reproduce the coefficients
mean and standard deviation, but they are not correlated as I had expected
given that I used the Cholesky coefficients to reproduce these correlations
I do not understand what I have done wrong?
Any help is welcomed.
Damien
DSTAT; RHS = MUBEN, MULAB, MUCAS; out=2$
--------+-------------------------------------------------------------------
--
| Standard
Missing
Variable| Mean Deviation Minimum Maximum Cases
Values
--------+-------------------------------------------------------------------
--
MUBEN| -3.7348 .408152 -5.023775 -2.357132 1000
0
MULAB| -.02753 .028474 -.117069 .048933 1000
0
MUCAS| -.015962 .015583 -.064371 .035926 1000
0
--------+-------------------------------------------------------------------
--
Descriptive Statistics for 3 variables
DSTAT results are matrix LASTDSTA in current project.
Correlations computed for 3 variables.
--------+--------------------------
Cor.Mat.| MUBEN MULAB MUCAS
--------+--------------------------
MUBEN| 1.00000 .04327 -.04466
MULAB| .04327 1.00000 -.01857
MUCAS| -.04466 -.01857 1.00000
I am really far off the model outputs
--------+--------------------------------------------
Cor.Mat.| ONE LA CA RI FEH
--------+--------------------------------------------
ONE| 1.00000 -.61706 -.83717 .07331 -.06425
LA| -.61706 1.00000 .23113 -.52217 -.23501
CA| -.83717 .23113 1.00000 .09078 -.16867
RI| .07331 -.52217 .09078 1.00000 .63762
FEH| -.06425 -.23501 -.16867 .63762 1.00000
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
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