MATLAB not enough input arguments

Question

I keep trying to run this and have no idea what is going wrong. I have it saved as test.m. I click run in the editor and in the matlab command window, it states not enough input arguments. I feel like I am missing something totally obvious, but I cannot spot the issue.

function y = test(A, x)
    %This function computes the product of matrix A by vector x row-wise
    % define m number of rows here to feed into for loop
    [ma,na] = size(A);
    [mx,nx] = size(x);
    % use if statement to check for proper dimensions
    if(na == mx && nx == 1)
        y = zeros(ma,1);   % initialize y vector 
        for n = 1:ma
            y(n) = A(n,:)*x;
        end
    else
       disp('Dimensions of matrices do not match')
       y = [];
    end
end

Answer 1

It is a function (not an script) and it needs some input arguments to run (in this case A and x), so you cannot hit the run button and expect it to run.

The first way:

Instead you can use the command windows in MATLAB and enter the command:

A = rand(3,3); % define A here
x = ones(3,1); % define x here
test(A,x) % then run the function with its arguments

remember that A and x should be defined properly.

The second way is:

Also you can hit the little triangle besides the green run button (see the figure below), and it will show you another option, type command to run. And there you can directly enter the same command test(A,x). After that, each time you just hit enter for this function and it runs this command instead of only the test command without any argument.

Answer 2

The third way:

function y = test(A, x)
%// TESTING CODE:
if nargin==0
    A = default_value_for_A;
    x = default_value_for_x;
end
... %// rest of the function code

This way allows you to "click the play button" and have your function run with no explicit input arguments. However, be advised that such a method should only be used:

• When debugging, so as not to allow users to call the function with no arguments if this is not its intended use case.
• If your function is not supposed to behave differently for a different number of inputs. See also function overloading in MATLAB based on number of input arguments.