Polynomial Interpolation in Matlab

Question

Sergey Dukman 2015-5-10

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回答： Joan Triadó 2022-2-4

Hei!

Can somebody help me with polynomial Interpolation in Matlab? I have a data set for x and y as vectors and N=15 as the order of polynomial.T o compute coefficient c I do as follows:

x=data(1,:);
>> y=data(2,:);
c=polyfit(x,n,14);

My question is what coefficient c is?

regards, Sergey

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Charles Garner 2020-9-26

my understanding is that C is arbitrary. Pick you own value.

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Answer 1

the cyclist 2015-5-10

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在 MATLAB Online 中打开

The output of polyfit is described in the very first sentence of the documentation here. Have you read that, and not understood it?

Also, in your code, what is n? Given how you have defined x and y, I would have expected your polynomial fit to be done with

polyfit(x,y,14)

Finally, I'm curious what your application of this is. I can't think of one where the fitting of a 15th-order polynomial is a good idea.

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Star Strider 2015-5-10

There must be a mathematical model of ethanol equilibrium available that estimates far fewer than 14 parameters from your 15 sets of data. Use that model, and fit it with one of the nonlinear parameter estimation functions (for example, nlinfit). It will give you a relatively accurate description of the process, and the estimated parameters will have physical meaning. As John has mentioned, throwing a 14-degree polynomial at it will likely confuse you more than enlighten you.

Charles Garner 2020-9-26

I am a co-author of a US Patent that uses curve fiitting. I think it is roughly 5th order. Patent #5706215. Related also to US Patent #5530925 In my telecom world, generally anything higher than 5 order isn't neccesary. You can play with it but it's not helpful.

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