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# coefficient determination of two variables

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Duy Hai Nguyen on 29 Jun 2020
Edited: Matt J on 4 Jul 2020
Hello everyone,
I would like to ask you some guidelines about how to solve this equation in matlab. This is an equation for an admittance of the open ended coaxial probe.
I would like to find the coefficients $\alpha$ and $\beta$ in the equation based on my measured data, in which those parameters are known: $\epsilon_r$, s, a and Y. The upper bound (N,M,P,Q) we can choose. For example, N=M = 4; P=Q=8.
I think some kind of fitting function might address my question, but I am really new to Matlab and have no ideas to do that.
Thank you very much,
Greetings
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### Accepted Answer

Matt J on 29 Jun 2020
lsqcurvefit would be one choice,
Note that your equation can be reorganized as a linear equation by multiplying through by the denominator expression involving the betas. That would likely be a good way fo developing an initial guess for the parameters.
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Matt J on 4 Jul 2020
Yes, the N and P you've passed in do not agree with the size of alphabeta. You should get in the habit of using dbstop
to probe such errors.

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