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Topic: Numerical integration of polyfit coefficients
Replies: 6   Last Post: Dec 12, 2013 5:50 PM

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Posts: 2,359
Registered: 12/6/04
Re: Numerical integration of polyfit coefficients
Posted: Dec 12, 2013 1:52 PM
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"Rajin " <> wrote in message <l8ctcd$jrp$>...
> Hello,
> I have the coefficients of a polynomial of order 12 given to me using polyfit (it was fitted to model a probability density function). I now need to use the given polynomial f(x), multiply it by x^2, and integrate it over a given boundary.
> I have tried using the integral function: integral(fun,xmin,xmax), where:
> fun = @(x) poly2sym(f) and f is the coefficients given by polyfit, but this doesn't work.
> Any ideas? Apologies if this seems trivial, I have tried everything!
> Thanks in advance,
> Rajin

The obvious first question is: "What do you mean by doesn't work?"
Any error message? Or just "looks" wrong.

It is not suprising you might get a non-sensical answer by trying to
integrate a 12 order polynomial. Try a different fitting function.

Look at the MathWorks curve fitting toolbox or try ezyfit from the MATLAB FEX:


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