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RE: st: Looping Enquiry


From   Nick Cox <n.j.cox@durham.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Looping Enquiry
Date   Thu, 29 Sep 2011 15:21:06 +0100

This is normally a good idea, but in this case the variable concerned is often negative, which to me implies that other methods have greater appeal. 

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

Valerie Orozco

The first idea that comes in my mind is to transform the problem.
If you think in a sum rather than in a product it will be easier to program it.
Indeed,  since the logarithm of a product is the sum of the logarithms, you can use it to program you formula easier in Stata.

score	transform to log	generate a cumulative sum	transform to exponential to have what you want 
x1	lnx1	                                         lnx1	                                                  x1
x2	lnx2	                                         lnx1+lnx2	                                                     x1x2
x3	lnx3	                                                  lnx1+lnx2+lnx3	              x1x2x3


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