is matlab 'fit' function changing behavior ?

I was working with curve fitting problem and use fit function as follows :

fit(x,y,fitType)

Now when I am running the code after 2 days, an error pops us saying there are more inputs than expected and correct syntax should be

fit(mdl,data)

I see that the second fit function was introduced in r2022b. does that mean the first fit function from curve fitting toolbox is getting replaced with something else ? If yes, what alternatives can I use in r2022b ?

Answer 1

[Hiro Yoshino]

There are actually many "fit" functions avaiable within MATLAB.

MATLAB determines which "fit" function to use based on the types and the combinations of the input arguments.

For example, the fit provided by Curve Fitting Toolbox is called this way:

load census;
f=fit(cdate,pop,'poly2')

f = 
     Linear model Poly2:
     f(x) = p1*x^2 + p2*x + p3
     Coefficients (with 95% confidence bounds):
       p1 =    0.006541  (0.006124, 0.006958)
       p2 =      -23.51  (-25.09, -21.93)
       p3 =   2.113e+04  (1.964e+04, 2.262e+04)

plot(f,cdate,pop)

whereas, the one provided by Predictive Maintenance Toolbox is:

load('linTrainVectors.mat');
mdl = linearDegradationModel;
fit(mdl,linTrainVectors)
mdl

mdl = 
  linearDegradationModel with properties:

                    Theta: 0.4982
            ThetaVariance: 0.0124
      SlopeDetectionLevel: 0.0500
                    Prior: [1×1 struct]
            NoiseVariance: 0.9920
    SlopeDetectionInstant: []
       CurrentMeasurement: 0
                      Phi: 2.5204
     InitialLifeTimeValue: []
     CurrentLifeTimeValue: []
         LifeTimeVariable: ""
             LifeTimeUnit: ""
            DataVariables: ""
                 UserData: []
              UseParallel: 0

I suppose the function that is available most among the toolboxes is "plot". You can find many plot functions.

Answer 2

[Xingzheng Pan]

Hey all. I still get trouble even use the demo case above. The Matlab still call the fit function in ML toolbox, any ideas to deactivate? I really need the fit function in curve fitting toolbox.

[Hiro Yoshino]

I bet you do not own the toolbox(es) required to run the code above.

You do not need deactivate toolboxes you have; MATLAB automatically selects the best one by checking the types and order of the arguments you give to the function.

[Xingzheng Pan]

Yeh mate. All fixed now. I realised I don't have curve fitting toolbox installed before.

Have a good day.