Depending on the context, you could code something like
transmorphic matrix chak(
real colvector dim1,
real colvector dim2,
| real colvector pop ,
real scalar b)
{
pointer scalar ppop
if (args()<3 | pop==.) ppop = &J(rows(dim1),1,1)
else ppop = &pop
... code using *ppop instead of pop ...
}
This allows the user to type
: chak(dim1, dim2, ., b)
This solution however assumes that pop=. is not a
meaningful input to chak().
ben
> -----Original Message-----
> From: [email protected] [mailto:owner-
> [email protected]] On Behalf Of U.A.QU.AP
> Sent: Tuesday, April 18, 2006 9:34 PM
> To: [email protected]
> Subject: Re: st: mata function : coding optional argument
>
> That is, there is no disponible solution of such problem.
> AbdelRahmen
>
> ---- Original message ----
> >Date: Tue, 18 Apr 2006 08:10:20 -0500
> >From: [email protected] (William Gould, Stata)
> >Subject: Re: st: mata function : coding optional argument
> >To: [email protected]
> >
> >AbdelRahmen El Lahga <[email protected]> writes,
> >
> >> I'm writing a mata function say:
> >>
> >> transmorphic matrix chak(real colvector dim1,
> >> real colvector dim2,
> >> | real colvector pop , real
> scalar b)
> >> {......}
> >>
> >>
> >> in which "pop" and the scalar "b" are optional arguments as
> >> you can see above
> >>
> >> My question is how to code the optional arguments. I want that
> >> if user dont specifies the vector "pop" mata must replace it
> >> by a vector of ones and similary for b.
> >> Following the help my solution was
> >>
> >> nb_arg=args()
> >> if (nb_arg<3) pop=J(rows(dim1),1,1)
> >> if (nb_arg<4) b=1
> >>
> >> but this solution don't allow the user to specifies the
> >> scalar b and omit the 3rd argument pop
> >
> >What AbdelRahmen has coded is exactly right, and Abdel is
> also right
> >that user can omit the third and fourth arguments, or the
> fourth, but
> >not just the third. Mata's arguments are positional, and
> positional
> >means that if you specify 3 argments, they are the first,
> second, and
> >third, not the first, second, and fourth.
> >
> >-- Bill
> >[email protected]
> >*
> >* For searches and help try:
> >* http://www.stata.com/support/faqs/res/findit.html
> >* http://www.stata.com/support/statalist/faq
> >* http://www.ats.ucla.edu/stat/stata/
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
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* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
