Solving large system of equations without explicit solution

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B K
B K 2011-9-14
Hello all,
I'm trying to develop a model in MATLAB for some of my data. I'm pretty much at my last point except what I thought would work, didn't. I have a set of 11 equations, each one a different datapoint evaluated at my input variables. Between these 11 equations, I have 8 constants that I need to solve for. MATLAB is irritated because I have more equations than variables and because there isn't an explicit solution. I know I won't be able to get values for my constants that satisfy all 11 perfectly. I thought "solve" would act like a regression and find the best fit given all 11 equations but evidently it doesn't. Is there a way to do what I want that I've missed?
Thank you for your time and assistance.

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回答（1 个）

Walter Roberson
Walter Roberson 2011-9-14
Sorry, solve() is part of the symbolic toolbox, and does not handle regressions.
The symbolic toolbox tool that would at first appear to be most appropriate would be stats::reg .
However, this will not necessarily be any better than MATLAB's usual nonlinear regression tools, if you already know the equations.
Please note that stats::reg is part of the MuPad standard library, and does not have a direct interface to MATLAB itself. To use it, you will need to use either evalin(symengine,....) or else feval(symengine,'stats::reg',....)
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Walter Roberson
Walter Roberson 2011-9-14
What form are the symbolic expressions? If they are polynomials then the coefficients can be extracted using coeffs or sym2poly.
B K
B K 2011-9-14
It's a polynomial! Coeffs just made my life beautiful. Thank you so much!

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