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<p>OK, forget my previous answer.</p>
<p>Use this:</p>
<p>function [n] = sellmeier(KL, lambda)<br>
K1 = KL(1); K2 = KL(2); K3 = KL(3);<br>
L1 = KL(4); L2 = KL(5); L3 = KL(6);<br>
lambdacarre = lambda.*lambda;<br>
foo1 = lambdacarre - L1;<br>
foo2 = lambdacarre - L2;<br>
foo3 = lambdacarre - L3;<br>
foo = 1./(foo1.*foo2.*foo3);<br>
n = sqrt(1 +...<br>
lambdacarre.*(K1*foo.*foo2.*foo3 + K2*foo.*foo1.*foo3 +
K3*foo.*foo1.*foo2));<br>
n=real(n);<br>
endfunction</p>
<p>Now it works.</p>
<p>Antoine</p>
<p>PS: Here is the issue: your sellmeier function should be
bulletproof and gracefully return real values no matter what
parameters you feed to it.<br>
</p>
<div class="moz-cite-prefix">Le 27/08/2020 à 16:52, Dang Ngoc Chan,
Christophe a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:AM0PR07MB393746021EE81DE351843C74E5550@AM0PR07MB3937.eurprd07.prod.outlook.com">
<pre class="moz-quote-pre" wrap="">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
<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Sellmeier_equation">https://en.wikipedia.org/wiki/Sellmeier_equation</a>
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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