What is the difference between polyfit and curve fitting

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Masoud Ghanbari
Masoud Ghanbari 2013-3-20
评论： Armani 2024-1-8
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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采纳的回答

Shashank Prasanna
Shashank Prasanna 2013-3-21
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
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.

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Matt J
Matt J 2013-3-20
POLYFIT applies to polynomial fitting only.
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Armani
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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