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#1 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 15:58:55

Hi;

I sent the data and detailed description of the model. Please let me know if anything is missing or ambiguous.

Many thanks!

#2 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 13:04:23

Hi bobbym

I have no secret project. Please give me your eamil and I will send you the data and the equations which I used to do these fittings.

Many thanks!

#3 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 12:47:22

Yes, I wish to get fits as good as the one on the right. In most cases I get fits between these two extremes.

In both cases I used 5 Fano profiles with a quadratic background. (Please refer to Fano resonance on Wiki)

#4 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 12:39:34

I attach examples for good and bad fits.

#7 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 12:05:51

All the data are in decimal double precision.

#8 Re: Coder's Corner » Simmulated Annealing and Lattice Boltzmann » 2013-01-01 12:03:47

Hi;

I googled but the stuff I found is rather confusing. I therefore decided to seek an expert advice rather than wasting my time trying.

#9 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 11:46:33

Hi

I appreciate your point and agree with most of your post, but my problem is different because first my data have a very distinctive shape (profiles sitting on a background) and not like your data which are scattered. My aim is to try to fit a curve to be as close as possible to the original data points. What I get from Levenberg-Marquardt in most cases is not an ideal fit because when I play with my initial values I get better fits (both visually and in a least squares sense). Because the model is complex and the data is large, I cannot afford playing with the initial values to get the 'best fit'. What I am looking for is some routine that is not easy to be trapped in local minima and could find its way to the global minimum spontaneously without interaction and manual adjustment.

#10 Coder's Corner » Simmulated Annealing and Lattice Boltzmann » 2013-01-01 11:11:57

JamesW
Replies: 7

Hi All

I am looking for a good code or software package to do Simmulated Annealing and Lattice Boltzmann. As I have no expertise in coding or using these numerical methods, it is strongly desirable that they are well documented and easy to use.

Thank you in advance for your help.

#11 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 11:07:45

Hi;

1) It is a least squares fit.

2) It consists of several Fano profiles (typically 5) superimposed on a logarithmic quadratic polynomial. It is not a simple model.

3) Between 3000-4000 points.

4) Typically 8 variables. The maximum is usually 13.

Do you think Octave, Maxima or geogebra can do this and which one would you recommend most.

By the way, I used Levenberg-Marquardt from numerical recipes and it sometimes produces a very good fit, but in most cases it goes wild. I tried many tricks but no one can do the fitting in all cases correctly.

Many thanks for your advice

#12 Re: Help Me ! » Good curve-fitting routine » 2013-01-01 10:08:25

Hi bobbym

Thank you for your reply. The problem with these general packages is that they are not flexible to use especially when the fitting model is too complicated. I spent several days in vain trying to do the fitting by Matlab. I don't think these packages can do better than Matlab.

#13 Help Me ! » Good curve-fitting routine » 2012-12-31 02:55:47

JamesW
Replies: 30

I am looking for a reliable curve fitting routine (preferrably in C or C++). Currently I use Levenberg-Marquardt routine from numerical recipes but it fails frequently. Your adivce will be appreciated.

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