What are all the ways to use name-value arguments in MATLAB code?

I want to accept name-value arguments in my matlab code. Also, some of the name-value arguments may be optional and may take default values specified by me.

Answer 1

[Ayush]

Hi @Nitu,

There are various ways for implementing name-value arguments.

Some of the ways are as follows:

• options argument

function res = func(a, b, options)
arguments
    a %constraints of a
    b %constraints of b
    options.c = 1 % default value
    options.d = 1 % default value
end
disp(a);disp(b);disp(options.c);disp(options.d);
end

Now, user can use the following syntaxes:

func(1,2);
func(1,2,'c',4); % a=1 b=2 c=4 (default value) d=1 (default value)
func(1,2,'d',3); % a=1 b=2 c=1 (default value) d=3
func(1,2,'c',3,'d',5); % a=1 b=2 c=3 d=5

• varargin

function res = func(a, b, varargin)
% access the arguments
for ind=1:2:numel(varargin)
    name=varargin{ind};
    val=varargin{ind+1};
    % do operations on these name-value arguments
end

% for pre-defined name-value arguments
% you can use input parser aswell
inp = inputParser;
% adding parameters
addParameter(inp, 'argName1', defaultValue, validationFcn);
addParameter(inp, 'argName2', defaultValue, validationFcn);
addParameter(inp, 'argName3', defaultValue, validationFcn);

%  parse the parameters
parse(inp, varargin{:});
% Access 
arg1 = inp.Results.argName1;
arg2 = inp.Results.argName2;

end

Now, user syntaxes:

func(1, 2, 'a', 2); % name-value argument : a=2
func(1, 2, 'c', 3, 'd', 4); % name-value arguments : c=3 and d=4

So, these were some ways to implement (optional) name-value arguments. You can read more about them here:https://www.mathworks.com/help/matlab/matlab_prog/validate-name-value-arguments.html

Hope it helps!

[DGM]

Nowhere did you actually demonstrate name=value syntax, and the code you pasted is not even complete enough to run or answer the question.

% let's rename everything and reorder the script and functions 
% so that it can at least be run
func1(1,2);

     1

     2

     1

     1

func1(1,2,'c',4); % a=1 b=2 c=4 (default value) d=1 (default value)

     1

     2

     4

     1

func1(1,2,'d',3); % a=1 b=2 c=1 (default value) d=3

     1

     2

     1

     3

func1(1,2,'c',3,'d',5); % a=1 b=2 c=3 d=5

     1

     2

     3

     5

func2(1, 2, 'a', 2); % name-value argument : a=2

Unrecognized function or variable 'defaultValue'.

Error in solution>func2 (line 35)
addParameter(inp, 'argName1', defaultValue, validationFcn);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

func2(1, 2, 'c', 3, 'd', 4); % name-value arguments : c=3 and d=4

function res = func1(a, b, options)
    arguments
        a %constraints of a
        b %constraints of b
        options.c = 1 % default value
        options.d = 1 % default value
    end
    % this displays positional arguments and key-value pairs
    disp(a);disp(b);disp(options.c);disp(options.d);
    % but nowhere is the output argument assigned any value
end

function res = func2(a, b, varargin)
    % access the arguments
    % why are we manually parsing varargin if we're using inputParser?
    % _neither_ of these two uses of varargin actually do anything
    for ind=1:2:numel(varargin)
        name=varargin{ind};
        val=varargin{ind+1};
        % do operations on these name-value arguments
    end
    
    % for pre-defined name-value arguments
    % you can use input parser aswell
    inp = inputParser;
    
    % adding parameters
    % obviously this isn't valid
    % none of these argument names, defaults, or functions 
    % are defined or relevant to the example
    addParameter(inp, 'argName1', defaultValue, validationFcn);
    addParameter(inp, 'argName2', defaultValue, validationFcn);
    addParameter(inp, 'argName3', defaultValue, validationFcn);
    
    %  parse the parameters
    parse(inp, varargin{:});
    
    % Access 
    % these aren't used for anything, and the output argument
    % is never assigned any value.
    arg1 = inp.Results.argName1;
    arg2 = inp.Results.argName2;
end