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st: RE: Using -collapse- extensively to find historical, irregular matches: Better way?


From   "Chih-Mao Hsieh" <Hsieh@olin.wustl.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Using -collapse- extensively to find historical, irregular matches: Better way?
Date   Tue, 30 Sep 2003 19:28:56 -0500

Nick,  Thanks for the tips.


The first suggestion that you mentioned, essentially the following:

. egen cited2 = group(cited) ;

. gen allcited = "" ;
. tostring citing ;
. tostring cited2 ;

. bysort citing (cited2) : replace allcited = allcited[_n-1] + " " +
cited2 ;
. by citing : keep if _n == _N ;
. bysort allcited (citing) : gen counter = _n - 1 ;
. sort citing ;

As can be expected, when it tries to do the first -bysort-, it returns
the error message "no room to add more variables due to width".  My
question is: Is there a best way to truncate the "concatenation" before
it goes over the max (presumably 255?), preferably without any loops?


Chihmao.

P.S. I tried the second option with reshape that you suggested -- it is
consuming much more computing time than this -bysort- method, so I will
stick with this.

-----------------------------------------------------
Chihmao Hsieh
John M. Olin School of Business
Washington University
Box 1133, One Brookings Drive
St. Louis, MO 63130
Email:  hsieh@olin.wustl.edu
http://students.olin.wustl.edu/~hsieh


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Tuesday, September 30, 2003 11:41 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: RE: RE: RE: RE: Using -collapse- extensively to find
historical, irregular matches: Better way?


Should be _n - 1, not _N - 1. 

Nick 
n.j.cox@durham.ac.uk 

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Nick Cox
> Sent: 30 September 2003 16:59
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: RE: RE: RE: Using -collapse- extensively to find 
> historical, irregular matches: Better way?
> 
> 
> Chih-Mao Hsieh
> > 	
> > 	I had been shying away from converting "cited" to
> > strings because the numbers are in the millions, i.e. 
> > strings would be length 7.  Many of the "citing" patents 
> > have more than 35-40 "cited" patents, and so the 
> > concatenation might surpass the string's length limit.
> > 	
> > 	Of course, the chances are not high that two patents
> > would match each other over the first 35 patents, so your 
> > way does appear to be better.
> 
> Another way is to -reshape-, something
> like this: 
> 
> bysort citing (cited) : gen j = _n
> reshape wide cited, i(citing) j(j) 
> bysort cited* (citing) : gen counter = _N - 1 
> 
> At this moment, I think that's a lot better
> than my earlier suggestions.
> 
> Nick
> n.j.cox@durham.ac.uk 
> 
> 
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