MATLAB: Curve fitting of fast-rising curve (power or sigmoid fit maybe)

Question

Hi,

Trying to fit a curve to the following data. I found the "sigm_fit" function on the matlab file exchange page but yet been able to use the fitted parameters in a model.

Thinking this is a power fit… but I'm not really sure, so that's why I'm asking here :P.

Any thoughts would be appreciated 😀

Answer 1

The best model is a mathematical description of the process that created your data, so consider that first.

Absent that, I would use a simple first-order exponential objective function to begin with

fcn = @(b,x) b(1) - b(2) .* exp(b(3).*x);

The initial parameter estimates would likely be:

b0 = [1; 1; -5];

This function will work in nlinfit and lsqcurvefit, and (with an extra line of code), fminsearch.