Start points for curve fitting are calculated in following ways:
- Starting points for some library models are determined heuristically if no start points (the default value of an empty vector) are passed to the fit function.
- For rational and Weibull models, and all custom nonlinear models, the toolbox selects default initial values for coefficients uniformly at random from the interval (0,1).
Similar question has been answered in community, please refer this link. For more details, please refer this doc link on StartPoint.
Hope this helps!