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