What is the difference between polyfit and curve fitting

Question

Masoud Ghanbari 2013-3-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/67959-what-is-the-difference-between-polyfit-and-curve-fitting

评论： Armani 2024-1-8

采纳的回答： Shashank Prasanna

在 MATLAB Online 中打开

Hi

What is the difference between polyfit and curve fitting ?

would you please see this page explain me these command:

modelFun =  @(p,x) p(3) .* (x ./ p(1)).^(p(2)-1) .* exp(-(x ./ p(1)).^p(2));
startingVals = [10 2 5];
coefEsts = nlinfit(time, conc, modelFun, startingVals);
xgrid = linspace(0,20,100);
line(xgrid, modelFun(coefEsts, xgrid), 'Color','r');

And The Page Is:

http://www.mathworks.com/products/statistics/examples.html?file=/products/demos/shipping/stats/cfitdfitdemo.html

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Masoud Ghanbari 2013-3-20

The typed command is on the selected page also

THNX

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Answer 1

Shashank Prasanna 2013-3-21

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I would encourage you to look at the documentation page of the functions you are you using to get a better idea of what each function is suited for.

POLYFIT:

http://www.mathworks.com/help/matlab/ref/polyfit.html

As Matt J mentioned is used to fit polynomials

NLINFIT:

http://www.mathworks.com/help/stats/nlinfit.html

Is non linear fitting/regression for models that need not be polynomials, but can be. Go through the examples in the above links to get a better idea.

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Matt J 2013-3-22

编辑：Matt J 2013-3-22

You need to decide first what kind of function gives a good model for your (x,y) data. If the (x,y) data come from a polynomial, use POLYFIT. If they come from a more complicated function, use NLINFIT.

Masoud Ghanbari 2013-3-28

Thanks Dear Matt J

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Answer 2

Matt J 2013-3-20

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https://ww2.mathworks.cn/matlabcentral/answers/67959-what-is-the-difference-between-polyfit-and-curve-fitting#answer_79341

POLYFIT applies to polynomial fitting only.

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Armani 2024-1-8

That's correct! POLYFIT is a function specifically designed for fitting polynomial curves to data.

POLYFIT returns the coefficients of the fitted polynomial. These coefficients can be used to create the equation of the polynomial curve, getaway shootout can then be used for various purposes such as prediction, interpolation, or smoothing.

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