setting a variable to the input

So I have this code, when I try to run it in the command window, it keeps saying too many input arguments.

I'm trying to set r=[] open incase I want to enter mutiple variabls.

ex:

command window

r=[ 2 4 5] or r=[ 2 4 6 7 8]

roots

it keeps coming back too many inputs arguments.

function roots
r=[];
roots(r)
end

[Tommy]

Sorry but can you explain a bit more what the goal is here?

I'm assuming you are trying to call this function with roots(r), but as you have named your function roots, MATLAB will instead call your function. And your function does not take any input arguments, so with roots(r) you are attempting to pass an input argument to a function that cannot accept an input argument.

[Jian Chen]

My original goal is to be able to have the user enter any amounts of the variables r and have it solve for roots, but then I just realized that I was adding extra steps to something thats already solved.

Thanks for explaining it to me.

Answer 1

[Robert U]

Hi Jian Chen,

The functionality that you describe cannot be done. Using object oriented programming the functionality could be close. With functions the call routine is different.

The function you write shadows the built-in command roots() anyway since it uses the same name. It does not make much sense to wrap an own function around a built-in function that is using the input unaltered. But for the sake of completeness there is an example for that below as well.

Functions - Mathworks Function Basics

function p = myRoots(r)
    validateattributes(r,{'numeric'},{'vector'});
    p = roots(r);
end

Call it by writing to command line for r = [3 -2 -4]:

myRoots([3 -2 -4])

Object oriented programming - Mathworks Classes Basics

Class "myClass.m"

classdef myClass   
    properties
        r; % factor representation of polynomial
    end
    
    methods
        function obj = myClass(r)
        % MYCLASS Construct an instance of this class
            if nargin == 1
                obj.r = r;
            elseif nargin > 1
                error('Too many inputs.')
            else
                % do nothing
            end    
        end
        
        function obj = set.r(obj,input)
        % set method for property "r", check validity of input
            validateattributes(input,{'numeric'},{'vector'});
            obj.r = input;
        end

        function p = roots(obj)
        % method "roots" returns polynomial roots of property "r" using built-in function "roots"
            p = roots(obj.r);
        end
    end
end

Working with the class to achieve same result as above:

myObject = myClass([3 -2 -4]);
myObject.roots

Kind regards,

Robert

[Jian Chen]

Yeah, I just reaized that i'm adding extra step to something thats aleady giving.

Thanks for the help.