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st: indirect evaluation of variables


From   Bill Rising <brising@louisville.edu>
To   "Stata Listserve" <statalist@hsphsun2.harvard.edu>
Subject   st: indirect evaluation of variables
Date   Sun, 30 Mar 2003 14:17:41 -0500

Hey Folks!

I've run into a situation where I'd like to build an expression which 
contains different variables depending on the observation. Now, this 
could be done by nesting a series of -cond()-s, though it would be a bit 
complex (and hard to generalize).

Is there some way to use variables a pointers (use indirect evaluation of 
the variables)? For example suppose that there were three variables:

bleen bling blam
ing      1    11
am       2    12
ing      3    13
ing      4    14

I'd like to be able to have

gen blob = eval("bl"+bleen), so that the dataset would then be

bleen bling blam  blob
ing      1    11     1
am       2    12    12
ing      3    13     3
ing      4    14     4

where the (non-existant) -eval()- function takes its string argument and 
interprets it as the name of a variable.

I vaguely recall being stumped by this once in the past, and know that 
I'm stumped once again. Any tips would be much appreciated, even negative 
ones.

Thanks,

Bill
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