I have written a Matlab R2020b function that optionally receives three inputs – but if the inputs are not received, they should be set to the defaults within the script.

function my_opt_func(opt1, opt2, opt3)
    if (~exist(opt1, 'var'))
        opt1 = setopt1();
    end
    if (~exist(opt2, 'var'))
        opt2 = setopt2();
    end
    if (~exist(opt3, 'var'))
        opt3 = setopt3();
    end

    disp(string(opt1) + string(opt2) + string(opt3))
    
    function opt1 = setopt1()
        opt1 = 1;
    end
    
    function opt2 = setopt2()
        opt2 = 2;
    end
    
    function opt3 = setopt3()
        opt3 = 3;
    end

end

Here, the different setopt functions are used to generate the appropriate default values.

Unfortunately, calling this function without parameters, as my_opt_func or my_opt_func() gives the error Not enough input arguments. I tried using a variant of varargin, but got the same error.

When I set the values without using the setopt functions, I don’t get this error – but due to the complexity of my actual program, I really need to use functions to develop my defaults.

How do I fix this error so that the user can call the function with or without parameters – as either my_opt_func() or my_opt_func(param1, param2, param3)?