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Zoid
Germany
5 Posts |
 Posted - 07/12/2011 : 1:26:19 PM
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Hi, everyone!
Does anyone know where to find a good tutorial for how to use the Fitting Function Builder in OriginPro 8.5? I´ve been trying to use this tool for several times now (using the "expression" mode), but even though the function itself seems to be of correct form the fit does not converge and/or Origin gives me an error message (or something like e.g. "Parameter initialization was called"). To be more specific, I´m dealing with a simple experiment where you measure the intensity of a beam of linear polarized light under different reflexion angles on a glass plane (Brewster angle, total reflexion etc.). The fitting function which I´d like to use is
y(x) = (n²cos(x)-Sqrt(n²-sin(x))/(n²cos(x)+Sqrt(n²-sin(x))
where y is the reflexion coefficient, n a relative reflexion index and x the angle of incidence of my light beam.
I chose A as the only parameter and identified it with n (reflexion index) to check if the given value n = 1.5 (reflexion index of glass) is correct or not.
Can anyone help me out with this? =)
Kindest regards,
Manfred
PS.: I managed to solve the problem in my last topic, even though I still don´t know how I did it (trial & error), merci to anyone who contributed. ;) |
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Zoid
Germany
5 Posts |
Posted - 07/12/2011 : 1:29:36 PM
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Oh, yeah...if anyone wants to give it a try, here is the data to be fitted:
=========
X-VALUES:
15
20
25
30
35
40
45
50
56
57
58
59
60
61
62
63
64
69
74
79
84
89
=========
=========
Y-VALUES:
0,178
0,181
0,17
0,158
0,143
0,121
0,097
0,041
0,039
0,041
0,045
0,052
0,062
0,07
0,078
0,094
0,107
0,19
0,305
0,454
0,654
0,8
=========
As already mentioned, the x-values are the different angles of incidence and the y-values are the reflexion coefficients which I calculated from the measured photo diode data...the function to be fitted can be found in the above post.
Thanks again to anyone who can help! |
Edited by - Zoid on 07/12/2011 1:33:32 PM |
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Working with the Fitting Function Builder