Polyfit Vs Fit command: what are the differences?

I would like to predict a quadratic curve (y=ax2 + bx + c) from a data set and the relative goodness of the fit model.

I used both the command polyfit (Polynomial curve fitting) and Fit (Fit the curve).

what is the difference between the two methods? Whit the second method I used 'normalize' but when I try to find the value with polyval the predicted data are no correct.

How can I test the goodness of the fit model if I use the command Poltyfit?

Thank you in advance

Answer 1

[Jyotsna Talluri]

Refer the below link to know the differences betwween fit and polyfit

https://www.mathworks.com/matlabcentral/answers/81143-fit-and-polyfit-lar-vs-least-squares

We cannot determine the goodness of fit using polyfit.Use fit function to determine the goodness of fit.

[fitobject,gof] = fit(x,y,fitType) 

returns goodness-of-fit in the structure gof.

[PRB]

Thank you!