How do i fix this error?

Here's my code, I'm trying to fit a arctangent function to data,

years = xlsread('C:\Users\a\Desktop\WorldPopulation', 'A1:CO1');
population = xlsread('C:\Users\a\Desktop\WorldPopulation', 'A2:CO2');
x = years.';
y = population.';

FO = fitoptions('Display','iter',...
    'StartPoint',[4100 0.02 -39.7 6500],...
    'MaxIter','2000',...
    'MaxFuncEval','3000');
FT = fittype('a.*atan(c.*x+d)+b', 'options', FO);
[min, gof] = fit(x, y, FT);

But I keep getting the error

Error using curvefit.basefitoptions/set
The name 'Display' is not an accessible property for an instance of class 'basefitoptions'.

Error in fitoptions (line 189)
        set(f,varargin{:});

Error in OptimizeCurve (line 15)
FO = fitoptions('Display','iter',...

How do i fix this?

Answer 1

[Stephan]

Hi,

the Display option is only avaiable if the fitting method is nonlinear least squares:

https://de.mathworks.com/help/curvefit/fitoptions.html?s_tid=doc_ta#bto9o6s-1-Display.

The default Method is 'None' (which appears strange). I would expect, that it works, when you set:

FO = fitoptions('Method', 'NonlinearLeastSquares', 'Display','iter',...
    'StartPoint',[4100 0.02 -39.7 6500], 'MaxIter','2000',...
    'MaxFuncEval','3000');

Best regards

Stephan