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st: RE: RE: sum in nonlinear equations


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: sum in nonlinear equations
Date   Tue, 30 Mar 2004 12:08:48 +0100

Needs tuning, as the -egen- call won't work. 

egen `X' = sum((_n < 34) * (_n*cos($B) + (_n-1)*tan($B)) )

is I think a step in the right direction. 

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

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Stephen P
> Jenkins
> Sent: 30 March 2004 11:42
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: sum in nonlinear equations
> 
> 
> How about something along the following lines? (untested!!)
> 
> Instead of 
> 
> gen `yh'= exp($A) + sum(from n =1 to 34)[n*cos($B)+ 
> (n-1)*tan($B)] -2 in
> 1
> 
> try
> 
> tempvar X
> egen `X' = (_n<=34)*sum( _n*cos($B) + _n-1*tan($B) )
> gen `yh'= exp($A) + `X' -2 in 1
> 
> Assuming your data set has at least 34 obs in it, the idea is 
> to use the
> egen to calculate the sum 
> 

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