Re: st: Error in function evaluator programs with nl

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

On 03/28/2012 11:32 AM, Guillaume Daudin wrote:

> Dear stata list users,
>
> I do not seem to be able to create a function evaluator program. I suppose I am missing something obvious…
>
> Here is the program :
>
> capture program drop nltc_add
> program nltc_add
> version 11
> 	syntax varlist (min=4 max=4) if, at(name)
> 	local prix_trsp21       : word 1 of `varlist'
> 	local prix_fob1         : word 2 of `varlist'
> 	local dist1     		: word 3 of `varlist'
> 	local contig1 			: word 4 of `varlist'
>
> 	tempname rho_ice rho_add rho_conti rho_conta
> 	scalar `rho_ice'=`at'[1,1]
> 	scalar `rho_add'=`at'[1,2]
> 	scalar `rho_conti'=`at'[1,3]
> 	scalar `rho_conta'=`at'[1,4]
> 	replace `prix_trsp21'= `dist1'^`rho_ice'*`rhoconti'*`contig1'+`dist1'^`rho_add'*`rhoconta'*`contig1'/`prix_fob1' `if'
> end
>
> But running :
>
> nl tc_add @ prix_trsp21 prix_fob1 dist1 contig1, parameters(rho_ice rho_add rho_conti rho_conta) initials(rho_ice 0.1 rho_add 0.3 rho_conti 0 rho_conta 0)
>
> gives me a r(198) error:
>
> nltc_add returned 198
> verify that nltc_add is a function evaluator program
>
> Thanks in advance for any help !


There are two bugs here.  First, the option to specify initial values is 'initial()', not 'initials()'.  Since -nl- does not accept an 'initials()' option, it passes that option onto your function evaluator program.  But your program does not accept an 'initials()' option, either, so it issues the error message.  -nl- gives you the flexibility to pass options to your evaluator program, but the cost is that -nl- itself cannot determine whether you misspelled one if its options or if you specified an option for your program.

The second issue is that you define the temporary scalars rho_conti and rho_conta, but you refer to rhoconti and rhoconta in your -replace- statement.

When I fix those two bugs, the program works with artificial data.


   -- Brian Poi
   -- bpoi@stata.com

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