How to fit data to my customized form automatically?

I have quite a few sets of data and I want to fit them to y=a-b*x^3. I know that I could use cftool and do it manually for each data set. But it is really tedious. Is it a better way to do it? Thanks a lot.

Answer 1

[Jiro Doke]

Since you're already using Curve Fitting Toolbox, use the underlying functions: fitttype and fit.

Example:

f = fittype('a-b*x^3', 'independent', 'x', 'coefficients', {'a', 'b'});
fitobj =  fit(rand(10,1), rand(10,1), f)

Alternatively, you can generate MATLAB code from cftool.

[Zhiting]

Nice~Thank you!

Answer 2

[Paulo Silva]

doc polyfit

[Zhiting]

I thought about polyfit. But I don't want to fit y=p3*x^3+p2*x^2+p1*x+p0. Instead, I want p2 and p1 to be 0. I don't see that I could specify this option in using polyfit.

[Paulo Silva]

you get the p values from polyfit

[Zhiting]

I want to fix p1 and p2 to be 0. I need y=p3*x^3+p0.