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# Re: st: mata function : coding optional argument

 From "U.A.QU.AP" <[email protected]> To [email protected] Subject Re: st: mata function : coding optional argument Date Tue, 18 Apr 2006 20:34:09 +0100 (CET)

```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]
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```

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