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From |
"Brian P. Poi" <brian@poiholdings.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Adjusting Brian Poi's nlsurquaid.ado by removing symmetry conditions and `at' in -nl- |

Date |
Wed, 23 Feb 2011 07:50:01 -0500 |

On 2/22/2011 9:35 PM, Alex Olssen wrote:

Dear Statlisters, My end goal is to estimate a nonlinear system of equations with adding up constraints similar to the QUAIDS model estimated by Brian Poi 2002 and 2008 in the Stata Journal. Now I am trying to make one adjustment at a time to nlsurquaids.ado to get a handle on altering this function evaluator program. Right now I am stuck trying to remove the symmetry conditions. I am not actually estimating a demand system and I do not want the Slutsky symmetry conditions. I altered nlsurquaids.ado by replacing all the lines that were similar to scalar `g21' = `g12' with scalar `g21'=`at'[1,10] and bumped the numbering of the [1,x] down for everything else so they didn't overlap. Removing symmetry conditions left me with 21 parameters to estimate as opposed to Poi's 15 - the symmetry conditions constrain 6 elements below the diagonal. I then changed the nlsur call from nlsur quaids @ ... param(a1 a2...) to include g21, g32 and g33 as parameters as they are no longer inferred from symmetry. However running the code now gives me the following error messages "could not evaluate equation 1 starting values invalid or some RHS variables have missing values" I have successfully made another adjustment earlier and it all worked fine. I actually don't understand what the `at' is really doing in function evaluator programs in -nl- . I read the documentation but didn't manage to pick up what `at' was doing from there on my own. Any help in explaining `at' or guidance with why my removal of symmetry conditions isn't working would be very much appreciated. Kind regards,

scalar `g21' = `at'[1,10]

-- Brian Poi -- brian@poiholdings.com * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: Adjusting Brian Poi's nlsurquaid.ado by removing symmetry conditions and `at' in -nl-***From:*Alex Olssen <Alex.Olssen@motu.org.nz>

**References**:**st: Adjusting Brian Poi's nlsurquaid.ado by removing symmetry conditions and `at' in -nl-***From:*Alex Olssen <Alex.Olssen@motu.org.nz>

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