use of fminunc with more than one variables

I am working to solve an uncostraint non-linear optimization using 'fminunc'

there are two versions

1.using a vector for different variables

>> fminunc(@(x)(x(1)-x(2)^0.4)/x(1), [1,2])

Solver stopped prematurely.

fminunc stopped because it exceeded the function evaluation limit,

options.MaxFunctionEvaluations = 200 (the default value).

ans =

1 2

2. using different variables

>> fminunc(@(x1,x2)(x1-x2^0.4)/x1, 1,2, 'options')

Unable to perform assignment because dot indexing is not supported for variables of this type.

Error in createOptionFeedback (line 33)

options.(stopTestOptions{k}) = [];

Error in prepareOptionsForSolver (line 57)

optionFeedback = createOptionFeedback(options);

Error in fminunc (line 156)

[options, optionFeedback] = prepareOptionsForSolver(options, 'fminunc');

As you can observe, the 1st version works, whereas 2nd fails.

What is the reason for this error, Is there way to make work the 2nd version ?

Thanks,

best regards,

Rahul

Answer 1

[Alan Weiss]

Please see the documentation on writing scalar objective functions.

If you have Release 2019a, you can also use the problem-based workflow, which would allow you to use two different control variables.

Alan Weiss

MATLAB mathematical toolbox documentation