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From rccrd....@gmail.com
Subject Re: [math] Usage of Marquardt Optimizer for an Equation
Date Sat, 12 Sep 2015 22:28:08 GMT
Ric ntendo dire: 1- che cosa gli hai detto ? 2- cosa ti hanno detto loro ?

Ric

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> On Sep 12, 2015, at 10:57 PM, Gilles <gilles@harfang.homelinux.org> wrote:
> 
> Hello.
> 
>> On Sat, 12 Sep 2015 13:12:36 +0200, Thom Brown wrote:
>> Hey,
>> 
>> I think I'm almost set up and I'm positive about my jacobian, but I can't
>> solve two - rather simple? - problems on my own.
>> 
>> double[] prescribedValues = new double[observedValues.length];
>>> for (int i = 0; i < prescribedValues.length; i++) {
>>>      prescribedValues[i] = observedValues[i];
>>> }
>> 
>> I don't know if that makes sense. All I do here is to set the target on my
>> observations. Because I can't think of another way to get observed "F"
>> values, but I think that's rather correct.
> 
> I'm not familiar with the problem itself ("triple exponential smoothing")
> so I'm a bit lost now with all the "previous period" and "previous season"
> etc.
> I hope I didn't put you on the wrong track.
> 
>> However:
>> 
>> 
>>> RealVector startVector = new ArrayRealVector(new double[] { 1.0, 0.0 });
>>> startVector.append(new ArrayRealVector(new double[] { 1.0, 0.0 }));
>>> startVector.append(new ArrayRealVector(new double[] { 1.0, 0.0 }));
>>> LeastSquaresProblem problem = new LeastSquaresBuilder().start(startVector
>>> ).model(distanceToCurrentF)
>>> .target(prescribedValues).lazyEvaluation(false
>>> ).maxEvaluations(1000).maxIterations(100).build();
>> 
>> 
>> this won't work.
> 
> Well you use arrays of size 2 as arguments while you have 3 parameters...
> I also don't understand the "append" calls...
> 
>> What I want to do is to set three points each for alpha,
>> beta and gamma that contain the possible values (0 <= alpha, beta, gamma <=
>> 1). Apparently equal entries are merged to one? Anyways, I also doubt I can
>> access my parameters by using:
>> 
>> Vector3D approx = new Vector3D(params.getEntry(0), params.getEntry(1),
>>> params.getEntry(2));
> 
> I don't see the purpose of using "Vector3D", the "RealVector" is already
> holding the values of the parameters; no need to copy them elsewhere.
> 
>> 
>> [...]
>> 
>> helper.calculateSmoothedObservation(i, approx.getX(), approx.getY(), approx
>>> .getZ());
>> 
>> 
>> at the very beginning of my jacobian function.
>> calculatedSmoothedObservation(int index, double alpha, double beta, double
>> gamma) should always update the S, b and I parameters by using the alpha,
>> beta and gamma values of the optimization. I think I'm not on the right
>> track here.
>> 
>> I'm positive that we (okay, you did more than I did here) can solve that
>> too :P
> 
> We can provide a few guidelines, but you should really look at the unit
> tests, and discover "what is what" in your problem...
> See also the function fitting classes in the package "o.a.c.m.fitting"; e.g.
> the "HarmonicCurveFitter" and its "AbstractCurveFitter" base class.
> 
> I looked a little at the code referred to in your other post. Some trivial
> suggestions:
> * Avoid "Double" when "double" would be fine.
> * Avoid variables named "l" (can easily be confused with "1").
> * Give meaningful names ("HelperClass" and "Test" do not describe what the
>  should do).
> * Comment abundantly. [Comments could help people help you...]
> * Devise unit tests for every case for which you can figure out the result
>  (or for which you have reference values).  Even trivial tests could point
>  you to where the code is getting off tracks.
> * Use a class to represent each concept of the problem at hand (this will
>  make the above "meaningless class name" problem vanish).
> 
> 
> Sorry if that does not help you find the solution directly,
> Gilles
> 
>> Greetings,
>> Thom
> 
> 
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