Re: st: nlsur function evaluator program QUAIDS with demographics

[olorunfemi sola <solafem7@yahoo.co.uk>]

Hi All,
Poi's command is the easiest and best  way to solve  demand system. Faria Hug claimed to have  estimated the 
elasticities with Poi command and have used bootstrap to obtain standard errors of the 
expenditure elasticity but  having trouble obtaining them for the 
compensated and uncompensated elasticities. But i think Poi is working on it. I think Poi himself will want to talk. I think Faria Hug is following this tread too.


Thanks





*********************************************************************** 
SOLA OLORUNFEMI   Ph.D
SENIOR LECTURER  
 DEAPARTMENT OF ECONOMICS
ADEKUNLE AJASIN UNIVERSITY 
AKUNGBA AKOKO 
ONDO STATE NIGERIA 
official e-mail: olorunfemi@adekunleajasinuniversity.edu.ng
TEL NO +234 803 581 0893 

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________________________________
From: Roberta Distante <r_distante@yahoo.it>
To: "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> 
Sent: Friday, 8 March 2013, 9:59
Subject: Re: st: nlsur function evaluator program QUAIDS with demographics

The problem of -quaids-  it does not allow one to have/compute standard errors of elasticities. That is why I was trying to write my program and estimate those through -nlcom-.

Thanks, anyway

Il giorno 08/mar/2013, alle ore 18:51, Jorge Eduardo Pérez Pérez <perez.jorge@ur.edu.co> ha scritto:

> You can use Brian Poi's recent command -quaids- to handle all these
> problems for you.
> 
> -ssc install quaids-
> _______________________
> Jorge Eduardo Pérez Pérez
> 
> 
> On Fri, Mar 8, 2013 at 10:39 AM, RD <r_distante@yahoo.it> wrote:
>> Dear Statalist-ers,
>> 
>> I am trying to write a function evaluator program using -nlsur- in Stata 12 to estimate a QUAIDS model (Banks et al., Restat 1997) with household demographics. So far, I had no success, as Stata returns an error message:
>> 
>> 'nlsurtry returned 199
>>    - di as error "verify that nlsur`eqn' is a function evaluator program"
>>    = di as error "verify that nlsurtry is a function evaluator program"
>> verify that nlsurtry is a function evaluator program
>>    - exit _rc'
>> 
>> I do not understand what I am doing wrong.
>> 
>> Also, copying the nlsurquaids program (st0029_1) by Brian Poi (2008) - which works properly - in a .ado file with a different name, placed in the same directory or in other directories "sysdir set", Stata returns the same exact error. I am puzzled.
>> 
>> Another silly question: is it possible to write a function evaluator program including, e.g., 15 "potential" demographic variables, but practically feeding it with, say, 7? I was wondering it because otherwise I should write different programs for different sets of demographics.
>> 
>> Last, but not least, when I use -nlcom- to compute elasticities, should I type variable mean values (for the full sample or for a subsample) to be multiplied to the coefficients or it is allowed to type variable names?
>> 
>> Here follows the code, slightly modified to include only one demographic variable (z1), which I plan to enlarge with more demographics.
>> 
>> Thanks in advance for your help.
>> 
>> 
>> // Demographics z_k enter as taste-shifters into the share equations and,
>> // to mantain integrability, are part of the a_i terms in the price index:
>> // ln[a(p)] = a_0 + sum_i[a_i + sum_k(a_ik*z_k)]*ln(p_i) +
>> // 1/2*sum_isum_j[g_ij*ln(p_i)*ln(p_j)]
>> // the model in share form looks like:
>> // w_i = a_i + sum_k(a_ik*z_k) + sum_j[g_ij*ln(p_j)] + b_i*ln[m/a(p)] +
>> // [l_i/b(p)]*ln[m/a(p)]^2
>> // where w_i=share of good i, p_i=price of good i, etc.
>> // b(p)=prod_i(p_i^b_i)
>> 
>> program nlsurtry
>> 
>> version 10
>> syntax varlist(min=9 max=9) if, at(name)
>> tokenize `varlist'
>> args w1 w2 w3 lnp1 lnp2 lnp3 lnp4 lnm z1
>> tempname a1 a2 a3 a4
>> scalar `a1' = `at'[1,1]
>> scalar `a2' = `at'[1,2]
>> scalar `a3' = `at'[1,3]
>> scalar `a4' = 1 - `a1' - `a2' - `a3'
>> tempname az11 az12 az13 az14
>> scalar `az11' = `at'[1,4]
>> scalar `az12' = `at'[1,5]
>> scalar `az13' = `at'[1,6]
>> scalar `az14' = -`az11' - `az12' - `az13'
>> tempname b1 b2 b3 b4
>> scalar `b1' = `at'[1,7]
>> scalar `b2' = `at'[1,8]
>> scalar `b3' = `at'[1,9]
>> scalar `b4' = -`b1' - `b2' - `b3'
>> 
>> tempname g11 g12 g13 g14
>> tempname g21 g22 g23 g24
>> tempname g31 g32 g33 g34
>> tempname g41 g42 g43 g44
>> scalar `g11' = `at'[1,10]
>> scalar `g12' = `at'[1,11]
>> scalar `g13' = `at'[1,12]
>> scalar `g14' = -`g11' - `g12' - `g13'
>> 
>> scalar `g21' = `g12'
>> scalar `g22' = `at'[1,13]
>> scalar `g23' = `at'[1,14]
>> scalar `g24' = -`g21' - `g22' - `g23'
>> 
>> scalar `g31' = `g13'
>> scalar `g32' = `g23'
>> scalar `g33' = `at'[1,15]
>> scalar `g34' = -`g31' - `g32' - `g33'
>> 
>> scalar `g41' = `g14'
>> scalar `g42' = `g24'
>> scalar `g43' = `g34'
>> scalar `g44' = -`g41' - `g42' - `g43'
>> tempname l1 l2 l3 l4
>> 
>> scalar `l1' = `at'[1,16]
>> scalar `l2' = `at'[1,17]
>> scalar `l3' = `at'[1,18]
>> scalar `l4' = -`l1' - `l2' - `l3'
>> 
>> quietly {
>> tempvar lnpindex
>> gen double `lnpindex' = 5 + `a1'*`lnp1' + `a2'*`lnp2' + `a3'*`lnp3' + `a4'*`lnp4' + `az11'*`z1'*`lnp1' + `az12'*`z1'*`lnp2' + `az13'*`z1'*`lnp3' + `az14'*`z1'*`lnp4'
>> 
>> forvalues i = 1/4 {
>> forvalues j = 1/4 {
>> replace `lnpindex' = `lnpindex' + 0.5*`g`i'`j''*`lnp`i''*`lnp`j''
>>          }
>>  }
>> tempvar bofp
>> gen double `bofp' = 0
>> forvalues i = 1/4 {
>> replace `bofp' = `bofp' + `lnp`i''*`b`i''
>> }
>> replace `bofp' = exp(`bofp')
>> replace `w1' = `a1' + `az11'*`z1' + `g11'*`lnp1' + `g12'*`lnp2' +  `g13'*`lnp3' + `g14'*`lnp4' + `b1'*(`lnm' - `lnpindex')  +  `l1'/`bofp'*(`lnm' - `lnpindex')^2
>> replace `w2' = `a2' + `az12'*`z1' + `g21'*`lnp1' + `g22'*`lnp2' +  `g23'*`lnp3' + `g24'*`lnp4' + `b2'*(`lnm' - `lnpindex')  +  `l2'/`bofp'*(`lnm' - `lnpindex')^2
>> replace `w3' = `a3' + `az13'*`z1' + `g31'*`lnp1' + `g32'*`lnp2' + `g33'*`lnp3'  + `g34'*`lnp4' + `b3'*(`lnm' - `lnpindex')  +  `l3'/`bofp'*(`lnm' - `lnpindex')^2
>> 
>> }
>> end
>> 
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