Re: st: constant in nonlinear squares

["Brian P. Poi" <bpoi@stata.com>]

On Tue, 3 Apr 2007, Maritza Sotomayor wrote:

> Dear statalist members:
> I'm trying to include a constant in a nonlinear function. I used the
> substitutable expression with Model 2 option -hasconstant- which
> needs a parameter. I generated a constant variable (column of ones,
> called constante) but I get an error r(498) "constante not found
> among parameters".
> -nl (iitt = 1/(1+exp(-1*{xb: constante lavrgdp ldpcgdp ltc
> lroyalsale latarif lagi lavgest ldcap}))),  nolog
> hasconstant(constante)-
> constante not found among parameters
> check hasconstant() option or try using nl without it
> r(498);
Maritza,

The hasconstant() option expects the name of a parameter, not the name of 
a variable.  Since you are using the notation {eqname:varlist} to specify 
a linear combination, in your case the parameter on the variable named 
constante will be xb_constante.  Thus, you would type

   . nl ... , hasconstant(xb_constante)

Hope this helps

  -- Brian Poi
  -- bpoi@stata.com

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