# st: RE: sum in nonlinear equations

 From "Stephen P Jenkins" To Subject st: RE: sum in nonlinear equations Date Tue, 30 Mar 2004 11:42:15 +0100

```How about something along the following lines? (untested!!)

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
>
> --
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```