st: How can I call a subroutine that's defined in another ado-file?

[Joseph Coveney <jcoveney@bigplanet.com>]

I noticed that the official Stata command -tetrachoric- has a subprogram
defined in it that I would like to use.  The subprogram is -PosDef-, which I
would like to use to perform matrix approximation after -polychoric-.  How
can I call -tetrachoric.PosDef- and feed it the polychoric correlation
matrix?

I've called -tetrachoric- with dummy data just to get the ado-file loaded
into memory, and that worked out okay--I can see it with -program list
tetrachoric.PosDef-.  But after running -polychoric- and copying the r(R)
into a matrix, say, R, I cannot successfuly feed that matrix
to -tetrachoric-'s -PosDef- subroutine.

That is, something like that below fails, yet I can confirm that the
subprogram still resides in memory.  Do I need to filch the code
from -tetrachoric- and copy it into a stand-alone ado-file?

Joseph Coveney

[output after initial use of -tetrachoric with dummy data omitted for
brevity]

. polychoric questionnaire_item*

. matrix R = r(R)

. local N = r(N) // for use in -factormat-

. tetrachoric.PosDef R
unrecognized command:  tetrachoric.PosDef invalid command name
r(199);

. PosDef R
unrecognized command:  PosDef
r(199);

. program list tetrachoric.PosDef

tetrachoric.PosDef, rclass:
 1.         args R
 2.         if !issym(`R') {
 3.                 error 505
 4.         }
 [output redacted for brevity]
22.         }

. program list PosDef
PosDef not found
r(111);

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