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st: nlcom and scalar give different results with same espression
From
Luca Fumarco <[email protected]>
To
"[email protected]" <[email protected]>
Subject
st: nlcom and scalar give different results with same espression
Date
Wed, 9 May 2012 22:03:46 +0200
Dear Statalister,
During some computation with the nlcom command, I come across the message "Maximum number of iterations exceeded", this is not a new thing for you statalisters (http://www.stata.com/statalist/archive/2009-03/msg01244.html).
As suggested in that past thread, I multiply my value by a large number and then I recover it in a next step.
However, when I double check the result by computing the same value with "scalar", the result is different.
This is what I write:
NLCOM version ->
nlcom (UNOBVARfirst: (1e+2)*normal((_b[_cons]+1*_b[Immig]+_b[experiment]*MeanEx)/exp(_b[lnsigma2:Immig]*1))-normal((_b[_cons]+0*_b[Immig]+_b[experiment]*MeanEx)/exp(_b[lnsigma2:Immig]*0))-predsndy*(_b[Immig]/exp(_b[lnsigma2:Immig]*1))), post
nlcom UNOBVAR: _b[UNOBVARfirst]/(1e+2)
****UNOBVAR= 0.1236019
SCALAR version ->
scalar UNOBVARcheck=normal((_b[_cons]+1*_b[Immig]+_b[experiment]*MeanEx)/exp(_b[lnsigma2:Immig]*1))-normal((_b[_cons]+0*_b[Immig]+_b[experiment]*MeanEx)/exp(_b[lnsigma2:Immig]*0))-predsndy*(_b[Immig]/exp(_b[lnsigma2:Immig]*1))
****UNOBVARcheck=-0.06785729
It occurs to me also in a couple of other instances.
Any idea?
Thank you for you time
Luca Fumarco
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