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There is no nesting here. It should suffice to cycle over the numerators
and find the matching denominators, or vice versa. 

Here is one way: 

foreach num of var q*num { 
	local den : subinstr local num "num" "den", all 
	local stub : subinstr local num "num" "", all 
	gen `stub' = `num' / `den' 
} 

Here is another way. This time we focus on getting the stubs by getting
a varlist of all the numerators and zapping the text "num". 

unab nums : q*num 
local stubs : subinstr local nums "num" "", all 

foreach s in local stubs { 
	gen `s' = `s'num/`s'den 
} 

As you can see, I don't trap any cases in which a numerator doesn't have
a matching denominator, or indeed vice versa, but that could be done. 

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

--- On Tue, 4/27/10, Dr. Bill Westman <bigweb_ddt@yahoo.com> wrote:

> From: Dr. Bill Westman <bigweb_ddt@yahoo.com>
> Subject: st: possible nested loop with multiple items
> To: statalist@hsphsun2.harvard.edu
> Date: Tuesday, April 27, 2010, 5:12 PM
> This is probably quite simple, but
> I've tried and failed a few times to write a working loop.
> 
> What I have isthe number of observations stored in
> variables representing numerators and denominators of
> several hundred questions.  The list has matched
> numerators and denominators, but each item has different
> numbers of letters (e.g.q_01a and q_01b, but q_02a-c). 
> Also numbers skip. 
> 
> q_01a_num
> q_01b_num
> q_02a_num-
> q_02x_num
> q_02a_den
> q_02b_den
> q_02x_den
> 
> I'd like to either loop through each item to 
> gen prop_`i' = q_***_num/q_***_den
> 
> or contract (if that is easier).  
> 
> Any suggestions would be appreciated.
> 
> Thanks!
> 
> Bill
> 
> 
>       
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