Re: st: Error in Poi's QUAIDS user-command

[Robin Winkler <robinwinkler@gmail.com>]

Thanks, Jorge. I was on version 1.0.1, which lacked the scalar.
I must have missed the update.
Robin

On 18 April 2014 20:33, Jorge Eduardo Pérez Pérez <jorge_perez@brown.edu> wrote:
> By the way, if the version is not the problem, consider moving this
> thread to the Statalist forum
>
> http://www.statalist.org/forums/
>
> as this list is being deprecated soon and Mr. Poi may not get to read
> the message.
> --------------------------------------------
> Jorge Eduardo Pérez Pérez
> Graduate Student
> Department of Economics
> Brown University
>
>
> On Fri, Apr 18, 2014 at 3:32 PM, Jorge Eduardo Pérez Pérez
> <jorge_perez@brown.edu> wrote:
>> Which version of -quaids- are you using? Mine is version 1.1.0 and the
>> code reads:
>>
>> if (quadratics == "") {
>> bofp = exp(lnp*beta')
>> lnpindex = lnp*alpha' :+ st_numscalar("e(anot)")
>> for(i=1; i<=rows(lnpindex); ++i) {
>> lnpindex[i] = lnpindex[i] + 0.5*lnp[i,.]*gamma*lnp[i,.]'
>> }
>> }
>>
>>
>> --------------------------------------------
>> Jorge Eduardo Pérez Pérez
>> Graduate Student
>> Department of Economics
>> Brown University
>>
>>
>> On Fri, Apr 18, 2014 at 2:43 PM, Robin Winkler <robinwinkler@gmail.com> wrote:
>>> Hi all,
>>>
>>> I believe I have found a serious error in the way in which the QUAIDS
>>> user command written by Brian Poi computes elasticities.
>>>
>>> In the Mata code underlying the ado file - the relevant bit is pasted
>>> below - the price index *lnpindex* used to compute the elasticities
>>> does not include alpha 0, which is entered into the command suite as
>>> *anot*. Hence, I have had the problem that  my price index was
>>> underestimated, and the magnitude of the computed expenditure
>>> elasticities tend to be way overstated.
>>>
>>> Should Mr Poi read this, I would be grateful for a comment.
>>>
>>> Robin
>>>
>>>
>>>
>>> *! version 1.0.0  29dec2011
>>> /*
>>> _quaids__utils.mata
>>> Mata routines called by
>>> nlsur__quaids.ado
>>> quaids_estat.ado
>>> quaids_p.ado
>>> */
>>>
>>> mata
>>>
>>> mata set matastrict on
>>>
>>> void _quaids__expelas(string scalar touses,
>>>      string scalar quadratics,
>>>      string scalar atmeans,
>>>      string scalar lnps,
>>>      string scalar lnexps,
>>>      real   scalar ndemo,
>>>      string scalar demos,
>>>      string scalar expelass)
>>> {
>>> real scalar i
>>> real vector alpha, beta, lambda, rho
>>> real vector bofp, cofp, lnpindex, lnexp, mbar
>>> real matrix gamma, eta
>>> real matrix shares, expelas, lnp, demo
>>> alpha  = st_matrix("e(alpha)")
>>> beta   = st_matrix("e(beta)")
>>> gamma  = st_matrix("e(gamma)")
>>> if (quadratics == "") {
>>> lambda = st_matrix("e(lambda)")
>>> }
>>> else {
>>> lambda = J(1, cols(beta), 0)
>>> }
>>> if (ndemo > 0) {
>>> eta = st_matrix("e(eta)")
>>> rho = st_matrix("e(rho)")
>>> if (atmeans == "") {
>>> st_view(demo=., ., demos, touses)
>>> }
>>> else {
>>> demo = mean(st_data(., demos, touses))
>>> }
>>> }
>>>
>>> if (atmeans == "") {
>>> st_view(shares=.,  ., st_global("e(lhs)"),  touses)
>>> st_view(expelas=., ., expelass, touses)
>>> st_view(lnp=.,     ., lnps, touses)
>>> st_view(lnexp=.,   ., lnexps, touses)
>>> }
>>> else {
>>> shares  = mean(st_data(., st_global("e(lhs)"), touses))
>>> lnp     = mean(st_data(., lnps, touses))
>>> lnexp   = mean(st_data(., lnexps, touses))
>>> expelas = J(1, cols(shares), .)
>>> }
>>> if (quadratics == "") {
>>> bofp = exp(lnp*beta')
>>> lnpindex = lnp*alpha'
>>> for(i=1; i<=rows(lnpindex); ++i) {
>>> lnpindex[i] = lnpindex[i] + lnp[i,.]*gamma*lnp[i,.]'
>>> }
>>> }
>>> else {
>>> bofp = J(rows(lnp), 1, 1) // 1, so now div0 problem
>>> lnpindex = J(rows(lnp), 1, 0)
>>> }
>>> if (ndemo > 0) {
>>> cofp = J(rows(lnp), 1, 0)
>>> for(i=1; i<=rows(lnp); ++i) {
>>> cofp[i] = lnp[i,.]*(eta'*demo[i,.]')
>>> }
>>> cofp = exp(cofp)
>>> mbar = 1 :+ demo*rho'
>>> for(i=1; i<=rows(expelas); ++i) {
>>> expelas[i,.] = 1 :+ 1:/shares[i,.]:*
>>> (beta + demo[i,.]*eta + 2*lambda/bofp[i]/cofp[i]*
>>> (lnexp[i]-ln(mbar[i])-lnpindex[i]))
>>> }
>>> }
>>> else {
>>> for(i=1; i<=rows(expelas); ++i) {
>>> expelas[i,.] = 1 :+ 1:/shares[i,.]:*
>>> (beta + 2*lambda/bofp[i]*(lnexp[i]-lnpindex[i]))
>>> }
>>> }
>>> if (atmeans != "") {
>>> st_matrix(expelass, expelas)
>>> *
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