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st: RE: sum in nonlinear equations


From   "Stephen P Jenkins" <stephenj@essex.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: sum in nonlinear equations
Date   Tue, 30 Mar 2004 11:42:15 +0100

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 

Stephen
-------------------------------------------------------------
Professor Stephen P. Jenkins <stephenj@essex.ac.uk>
Institute for Social and Economic Research
University of Essex, Colchester CO4 3SQ, U.K.
Tel: +44 1206 873374.  Fax: +44 1206 873151.
http://www.iser.essex.ac.uk   


> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu 
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of 
> Andreas Aschbacher
> Sent: 30 March 2004 09:37
> To: statalist@hsphsun2.harvard.edu
> Subject: st: sum in nonlinear equations
> 
> 
> Dear fellows !
> is there apossibility to write line *9* in Stata-code - 
> I have written it in pseudocode,please look at line 9 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> . capture program drop nlfaq
> 
> . program nlfaq
>   1.    if "`1'" == "?" {
>   2.       global S_1 " A B C"
>   3.       global A=1
>   4.       global B=1
>   5.       global C=1
>   6.       exit
>   7.    }
>   8.    tempvar yh  
>   9.    gen `yh'= exp($A) + sum(from n =1 to 34)[n*cos($B)+ 
> (n-1)*tan($B)] -
> 2 in 1
>  10.    replace `yh'= $A/$B +$C^2-log($B) in 2
>  11.    replace `yh'= $A/($A+$B+$C)- sin($C) in 3
>  12.    replace `1' = `yh'
>  13.    
> . end
> 
> . nl faq y ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> this would be very necessary for me because I could 
> deconvolute with Stata using modified Simpsonrule for 
> computing integrals. using LevenbergMarquardt with Stata is 
> possible in physics,convolution- computing is very easy 
> too,the way back namely deconvolution would be possible too 
> if I could compute this sum
> 
> any help would be appreciated very much
> andreas aschbacher,greetings to all fanatic Stata users in the world
> 
> -- 
> +++ NEU bei GMX und erstmalig in Deutschland: TÜV-geprüfter 
> Virenschutz 
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> http://www.gmx.net/virenschutz
> 
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