Undefined function or variable

I tried the CSP program from this file exchange : https://www.mathworks.com/matlabcentral/fileexchange/22915-common-spatial-patterns but whenever i try the CSP function which is this one:

%   CSP Function
%   Coded by James Ethridge and William Weaver
function [result] = CSP3(varargin)
    if (nargin ~= 2)
        disp('Must have 2 classes for CSP!')
    end
    Rsum=0;
    %finding the covariance of each class and composite covariance
    for i = 1:nargin 
        %mean here?
        R{i} = ((varargin{i}*varargin{i}')/trace(varargin{i}*varargin{i}'));%instantiate me before the loop!
        %Ramoser equation (2)
        Rsum=Rsum+R{i};
    end
    %   Find Eigenvalues and Eigenvectors of RC
    %   Sort eigenvalues in descending order
    [EVecsum,EValsum] = eig(Rsum);
    [EValsum,ind] = sort(diag(EValsum),'descend');
    EVecsum = EVecsum(:,ind);
    %   Find Whitening Transformation Matrix - Ramoser Equation (3)
        W = sqrt(inv(diag(EValsum))) * EVecsum';
    for k = 1:nargin
        S{k} = W * R{k} * W'; %       Whiten Data Using Whiting Transform - Ramoser Equation (4)
    end
    % Ramoser equation (5)
   % [U{1},Psi{1}] = eig(S{1});
   % [U{2},Psi{2}] = eig(S{2});
    %generalized eigenvectors/values
    [B,D] = eig(S{1},S{2});
    % Simultanous diagonalization
			% Should be equivalent to [B,D]=eig(S{1});
    %%%%%verify algorithim
    %disp('test1:Psi{1}+Psi{2}=I')
    %Psi{1}+Psi{2}
    %%%%%sort ascending by default
    %[Psi{1},ind] = sort(diag(Psi{1})); U{1} = U{1}(:,ind);
    %[Psi{2},ind] = sort(diag(Psi{2})); U{2} = U{2}(:,ind);
    [D,ind]=sort(diag(D));B=B(:,ind);
    %Resulting Projection Matrix-these are the spatial filter coefficients
    result = B'*W;
end

it keeps giving me this error:

>> CSP3
Must have 2 classes for CSP!
Warning: Matrix is singular to working precision. 
> In CSP3 (line 27) 
Undefined function or variable 'S'.
Error in CSP3 (line 42)
    [B,D] = eig(S{1},S{2});
    

or else if there's any other useful CSP file i'll be very grateful, thank you.

[KSSV]

What input you tried?

[Yasyas9]

My inputs are going to be signals

[meghannmarie]

Are you giving it any inputs? If I do not give the funtion any inputs it gives me that error:

CSP3()

If I put numbers in it works:

CSP3(1,2)

[Yasyas9]

thank you meghannmarie

[Yasyas9]

that was helpful