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st: RE: LevenbergMarquardt/summary


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: LevenbergMarquardt/summary
Date   Tue, 9 Mar 2004 10:16:12 -0000

It might be better to set this up as a -ml- problem. 

The text of Sophia Rabe-Hesketh and Brian Everitt
discusses the two Gaussians case in detail and poses
your case as an exercise, with hints for solution. 

http://www.stata.com/bookstore/statanalyses.html

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

Andreas Aschbacher

> In austrian centre of physics we use Stata to do
> LevenbergMarquardt(nl-coomand)
> please look at my posting from january 20th with  
> heading:LevenbergMarquardt
> short summary :the number of persons who is exposed to a little 
> dosis-interval /about 0.01 mSv/ yields in sum a curve which is mostly
> composed of 
> two sometimes three humps.above each dosis-interval /about 
> 0.01 mSv/there is
> the number 
> of persons as function. with Stata it was possible to show that in 397
> cases we have the sum of Gau-distributions.the results are 
> very useful.
> because of lv-command we can talk here about skewness of our curves.
> median-test is also used very often.we decided to take Stata 
> to use for our
> work becaue it is so easy to split in subgroups and make tests after.
>                                 -
> 
> My question: if I have two Gau-curves to be fitted,it is no 
> problem to find
> values
> in Stata.but if I have to find three Gau-curves,I mean to 
> come from 1) to
> 2) for
> example
> 
> 1)
> Ai for i = 1,2.... means amplitude
> A1	12209.2
> 1	4.382678
> delta1	0.3097696
> A2	21683.69
> 2	4.200002
> delta2	0.550282
> 
> 2)
> A1	11509.05
> 1	4.403567
> delta1	0.3050716
> A2	1305.195
> 2	4.18422
> delta2	1.100233
> A3	21540.19
> 3	4.198081
> delta3	0.5104234
> 
> I need long time to try.with another famous statistical 
> software I have
> possibility to make 
> constraints and it takes no long time.
> I "fear the worst" that someone(my boss?) will ask me during my
> presentation,if there are add-inns in Stata to use or 
> user-written-programs that I have
> this feature.
> it is a pity that it is not possible for me to come to 2nd 
> German Stata
> User's meeting in April.

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