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Re: st: Mata function stata() within program


From   M Hollis <m73hollis_stata@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Mata function stata() within program
Date   Fri, 24 Mar 2006 08:11:04 -0800 (PST)

Thanks for the patient explanations.  I completely
misread the sets of quotes.  I realize now that it was
just a simple case of concatenation.

--- Nick Winter <nw53@cornell.edu> wrote:

> This seems right to me.  The only thing I'd add is
> that the plus 
> signs are not "enclosing" the x and y; they are
> simply the 
> concatenation operator.
> 
> In regular Stata, you can do the same thing to put
> strings together:
> 
> . local x = "abc" + "def"
> 
> . di "`x'"
> abcdef
> 
> Or you can concatenate two string variables:
> 
> . generate myvar = var1 + var2
> 
> and so on.
> 
> --Nick Winter
> 
> 
> At 11:40 AM 3/23/2006, you wrote:
> >M Hollis wrote:
> > > --- "William Gould, Stata" <wgould@stata.com>
> wrote:
> > > > My suggested solution is
> > > >
> > > > stata("local hash1 = mod("  +  key1  +  ",
> 197)")
> > >
> > > Thanks for your detailed discussion about mata
> vs. ado
> > > files.  Very helpful.  I was wondering, though,
> if you
> > > could provide a manual reference or more of a
> > > description of the syntax in your suggested
> solution
> > > above.  In particular, I'm wondering what the "
> + key1
> > > + " is doing exactly.  I haven't run across that
> > > option in the manual, and it's hard to search
> the help
> > > for something that's just quotes and plus signs.
>  I
> > > feel like it could be a very useful function if
> I
> > > could figure out how it works.
> >
> >Not that I am competent, but I think I can answer
> your question partly. Bill
> >might step in to correct me if I were wrong.
> >
> >In general, you have to put a string within the
> parentheses of stata(), hence
> >you have to state:
> >
> >: stata("local hash1 = mod(1,197)")
> >
> >Now, consider the situation that you want to change
> the code to something
> >saying
> >
> >: stata("local hash1 = mod(x,y)")
> >
> >where x and y  are Mata variables. As it stands x
> and y not get "expanded",
> >because they are enclosed in quotes. Hence Stata
> would see
> >-local hash1 = mod(x,y)- which will give an error.
> Bills trickery now is to
> >close the quotation before x, than plug in x as a
> Mata Function, and finally
> >put the rest of the command in quotes again. Hence
> is code should read as
> >
> >: stata(
> >         "local has1 = mod"   // <- within qoutes
> >            x                 // <- without qoutes
> >          ", "                // <- within qoutes
> >            y                 // <- without qoutes
> >          ")"                 // <- within quotes
> >         )
> >
> >But that is only the first part of the idea. The
> second part is, that x and y
> >has to be "enclosed" between + signs.
> >
> >: stata(
> >         "local has1 = mod"
> >          + x +               // <- within +
> >          ", "
> >          + y +               // <- within +
> >          ")"
> >         )
> >
> >Don't ask me why, but it works ;-). Probably that
> way Mata knows that it has
> >to calculate something. Maybe someone else can take
> over for the explanation.
> >
> >Uli
> >
> >--
> >kohler@wz-berlin.de
> >+49 (030) 25491-361
> >*
> >*   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/
> 
>
________________________________________________________
> Nicholas J. G. Winter                    
> 607.255.8819 t
> Assistant Professor                      
> 607.255.4530 f
> Department of Government             
> nw53@cornell.edu e
> Cornell University       
> falcon.arts.cornell.edu/nw53 w
> 308 White Hall
> Ithaca, NY 14853-4601 
> 
> 
> *
> *   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/
> 


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