Re: st: Need help on using external global in st_view to avoid recompiling in Mata

[Nick Cox <njcoxstata@gmail.com>]

I would not think this way. Write your code to take what varies as an
input argument.

Nick

On Fri, Mar 30, 2012 at 4:32 PM,  <Jean-Francois.Bertrand@fin.gc.ca> wrote:

> I have written a Mata function to use with -moptimize- or -ml- to estimate
> a discrete labour supply model.  The simplified example below works for data where
> I would have 3 distinct hours choice (e.g. 0 hours, 20 hours and 40 hours) with
> income for each choice.
>
> ----
>
> version 11.2
>
> mata:
>
> function LSmodel_d0(transmorphic scalar M, real scalar todo, real rowvector b, real scalar lnf, real rowvector g, real matrix H)
> {
>        real colvector beta_y, beta_h
>
>        real colvector U
>        real colvector sum_eU
>        real colvector y_chosen
>        real colvector h_chosen
>
>        real colvector L_1
>
>        real matrix y_i
>        real matrix h_i
>
>        beta_y          = moptimize_util_xb(M,b,1)
>        beta_h          = moptimize_util_xb(M,b,2)
>
>        st_view(y=.,.,"y_chosen")
>        st_view(h=.,.,"h_chosen")
>
>        st_view(y_i=.,.,("y0","y20","y40"))
>        st_view(h_i=.,.,("h0","h20","h40"))
>
>        U  = beta_y:*y_chosen :+ beta_h:*h_chosen
>
>        U_i  = beta_y:*y_i :+ beta_h:*h_i
>
>        sum_eU = quadrowsum(exp(U_i))
>
>        L_1 = (U :- ln(sum_eU))
>
>        lnf = moptimize_util_sum(M,L_1)
> }
>
> mata mosave mata_LS_singles_quad_d2(), dir(PERSONAL) replace
>
> end
>
> ----
>
> Since I might use different hours choices for different group of the population (as done
> in the economic literature), I would like to avoid having to recompile the code if
> I want to run my estimator on, for example, 5 distinct hours choice (e.g. 0 hours,
> 10 hours, 20 hours, 30 hours and 40 hours) so that:
>
> st_view(y_i=.,.,("y0","y10","y20","y30","y40"))
> st_view(h_i=.,.,("h0","h10","h20","h30","h40"))
>
> I was thinking of defining a global macro that could vary depending on the data I use.
> For example, I could use:
>
> global h_i = `""h0","h20","h40""'
>
> or
>
> global h_i = `""h0","h10","h20","h30","h40""'
>
> depending on the data used.
>
> Is it possible?
>
> My attempts to use pointers and global macro (-findexternal()- or -valofexternal()-)
> have not worked so far.

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