Problems with the three-parameter Weibull distribution

Hi, I am working with the three-parameters Weibull distribution because my dataset contains only negative numbers. The code below is found in the documentation and obviously works correctly.

Three-Parameter Weibull Distribution - MATLAB & Simulink - MathWorks United Kingdom

However, I don't fully understand how it works. I have searched on-line and in the documentation but I can't get around the two lines that I have highlighted in bold. I don't understand how to assign the values to the start vector and how to assign values to lower and upper bound. Any reference to the 'Weight' data would be helpful.

Thank you

Kind Regards

Federico

load carsmall

x = linspace(0,6000);

f_def = @(x,a,b,c) (x>c).*(b/a).*(((x-c)/a).^(b-1)).*exp(-((x-c)/a).^b);

try

mle(Weight,'pdf',f,'Start',[1700 2 1500])

catch ME

disp(ME)

end

opt = statset('FunValCheck','off');

params = mle(Weight,'pdf',f,'Start',[1700 2 1500],'Options',opt, ...

'LowerBound',[0 0 -Inf],'UpperBound',[Inf Inf min(Weight)])

figure

histogram(Weight,8,'Normalization','pdf')

hold on

plot(x,f(x,params(1),params(2),params(3)),'LineWidth',2)

hold off

Answer 1

[Federico Antonelli]

I have recently installed R2021b and the code given in the documentation works correctly. I have been able to find the parameters gamma, eta and beta without any problems.The software version was the issue.

Kind Regards

Federico