ParmHat not returning shape parameter

Hello,

I'm new to MATLAB and statistics, but have been trying to estimate my parameters for a weibull distribution of a set of value. When I run the command parmHat=wblfit(x), it should technically return both scale and shape parameter, but its returning only the former. Why is it so?

My x data= [221447,277196,464274,565756,463453,564535,653655,564354,576124,567234,896453] fro example.

Regards

Answer 1

[Star Strider]

It returns both parameters for me (in R2020a, Update 5):

data= [221447,277196,464274,565756,463453,564535,653655,564354,576124,567234,896453];
parmHat = wblfit(data);
Shape = parmHat(1)
Scale = parmHat(2)

producing:

Shape =
          588194.482822158

Scale =
          3.35979418647355

.

[Chaman Srivastava]

Hello,

Thank you very much for the swift response.

I'm updating mine to R2020a, Update 5 now. But the command runs on the older version as well.

I still don't understand that why the function parmHat=wblfit(data) doesn't return both scale and shape parameter which is contrary to what is mentioned in Matlab manual https://se.mathworks.com/help/stats/wblfit.html? Any insights on this?

[Star Strider]

My pleasure!

The wblfit function returns both, as my code demonstrates. (See the documentation for details.) They are both returned as elements of the same output vector, ‘parmHat’ in my code. They are not returned as separate outputs, as is true for normfit, for example.

[Chaman Srivastava]

Thanks again! Just a small comment for people reading this answer:

output 1 is scale parameter and output 2 is shape! :)

[Star Strider]

The documentationi is a bit confusing in that regard:

• parmHat = wblfit(x) returns the estimates of Weibull distribution parameters (shape and scale), given the sample data in x.

I assumed that they were in that order, although in Output Arguments, parmHat states:

• Estimate of the parameters a (scale) and b (shape) of the Weibull distribution, returned as a row vector.

Reading further in the documentation is always beneficial!

[Chaman Srivastava]

Indeed. Thanks for the help.

[Star Strider]

As always, my pleasure!