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

[<Jean-Francois.Bertrand@fin.gc.ca>]

Hello all,

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.

Regards,
Jean-François Bertrand





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