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RE: st: looping across an unknown number of columns


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: looping across an unknown number of columns
Date   Tue, 10 Aug 2004 11:54:40 +0100

Two kinds of answer: 

1. As you -reshape- to wide a variable name like 
-foo- will become the stub of a set of 
variable names, so in many cases a wildcard like 
-foo*- will be sufficient to characterise 
the set. That wouldn't be precise enough if 
you also had e.g. -foot-. You might need 
e.g. -foo????-. 
 
Typically you can loop over such 
a set of variables using -foreach- without 
knowing how many of them exist. One way to 
count them would be 

unab foo : foo* 
local nvars : word count `foo' 

2. It may be that what you want to do 
is much more efficiently done within the long 
structure before the -reshape-, or without the 
-reshape-. 

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

Jason Rachlin
> 
> I am reshaping my data so each date becomes a column.  I will 
> not know how many
> dates are in my dataset and thus will not know how many 
> columns I have.  I'd like
> to loop across the columns performing an operation once for each date.
> 
> > program then loops over these dates performing a function.  
> I'd like to loop
> > until I hit the last date in my dataset which will change 
> each time I run the
> > program depending on the size of the dataset.  Can someone 
> please recommend an
> > efficient way to identify my last column so I can define NumDays?
> >
> > local NumDays = ?
> > local i = 1
> > while `i' <= NumDays {
> >     ...
> > }
> >

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