[Scilab-users] Weird error with leastsq()

[Dang Ngoc Chan, Christophe]

Hello all,

Let's talk about optics.
I have a glass, its refraction index n varies with the wavelength lamba.
I have a CSV file with the corresponding data (verre_HOQ.cvs attached), 52 points.

I want to model this with the Sellmeier model
https://en.wikipedia.org/wiki/Sellmeier_equation
and use for this the attached script (regression_sellmeier.sce).

Mind to set the path at line 7 of the script if you want to run it.

My problem:
I can run piecewise regression,
i.e. it runs when I work with the points 1 to 25, 13 to 39, or 32 to 52;
e.g. at lines 11 and 12, it works when I use

// ----------

lambda = 1e-3*donnees(1:25, 1); // en µm

nexp = donnees(1:25, 2);

// ----------

but when I try to extend these ranges (and of course when I try to use all the points),
it fails with the following error:

5215700pt: Wrong type for output argument #1: Real scalar expected.

Can anyone tell me what goes on here?

Regards

--
Christophe Dang Ngoc Chan
Mechanical calculation engineer


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