function [a,b] = find_com(x,y,A)
%x = checkx; y = checky; A = roi_basic;
%nargin = 1; x = roi_new;
% Finds centre of mass of matrix A in x, y index notation

if nargin == 1
    A = x;
    [Ar Ac] = size(A);
    x = 1:Ac;
    y = (1:Ar)';
else
    y = y(:);
    x = (x(:))';
end

sumA = sum(A(:));
if sumA == 0
    a = 0;
    b = 0;
else
    [row col] = size(A);
    % Find centroid across columns:
    temp = A.*(ones(row,1)*x);
    a = sum(temp(:))/sumA;
    % Across rows:
    temp = A.*(y*ones(1,col));
    b = sum(temp(:))/sumA;
end