MATLAB: What does fitoptions ‘Method’ = ‘None’ mean

curve fittingoptimization

I just looked up the defaults for fitoptions. For 'Method' the default appears to be 'None'.
>> fitoptions
ans =
    Normalize: 'off'
      Exclude: [1x0 double]
      Weights: [1x0 double]
       Method: 'None'
But what does that mean? It has to use SOMETHING to determine whether it has found the best fit. I can't seem to find out what, though. I'm very curious about this now.

Best Answer

Alright! This is it:
        Normalize: 'off'
          Exclude: []
          Weights: []
           Method: 'NonlinearLeastSquares'
           Robust: 'Off'
       StartPoint: [1×0 double]
            Lower: [1×0 double]
            Upper: [1×0 double]
        Algorithm: 'Trust-Region'
    DiffMinChange: 1.0000e-08
    DiffMaxChange: 0.1000
          Display: 'Notify'
      MaxFunEvals: 600
          MaxIter: 400
           TolFun: 1.0000e-06
             TolX: 1.0000e-06
So as it turns out, it's a nonlinear least-squares approach with the trust region algorithm. The options-object seems to be always initialized like this. After that, the user-input is checked for an options-arguments to overwrite/edit it with.
Thanks again for pointing me in the right direction!
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