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st: Re: RE: Re: RE: Re: RE: Multiple commands under "By varlist"?


From   "Subhankar Nayak" <nayak@bellsouth.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: RE: Re: RE: Re: RE: Multiple commands under "By varlist"?
Date   Sat, 26 Jun 2004 11:31:16 -0400

Right. I saw your point, but I did word myself very inefficiently!

----- Original Message ----- 
From: "Nick Cox" <n.j.cox@durham.ac.uk>
To: <statalist@hsphsun2.harvard.edu>
Sent: Saturday, June 26, 2004 11:06 AM
Subject: st: RE: Re: RE: Re: RE: Multiple commands under "By varlist"?


> Yes and no. Sorry to repeat the point, but you 
> put the blame in the wrong place again
> in talking of the inefficiency of -while-, 
> which is just a framework and not to blame 
> for what's inside. 
> 
> The ineffiency of -while- is in going (e.g.)
> 
> local i = 1 
> while `i' < 1000 { 
> ...
> local i = `i' + 1 
> } 
> 
> rather than (say) 
> 
> forval i = 1/1000 { 
> ...
> }
> 
> -- although note that not every -while- 
> can be made a -forval- --
> 
> but that's small beer compared with the 
> possible inefficiency of what the user 
> puts within the loop, which is the issue here. 
> 
> Nick 
> n.j.cox@durham.ac.uk 
> 
> Subhankar Nayak
> > 
> > Yes, that's a very interesting point that I had missed.
> > I now see why -while- is so inefficient: it reads such a huge 
> > fraction of
> > unneccesary observations. I can avoid that by more efficient 
> > treatment of
> > the observation: avoid reading all those unneccesary observations
> > repeatedly.
> 
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