%ISSYM Checks whether a matrix is symmetric
%
% OK = ISSYM(A,DELTA)
%
% INPUT
% A Dataset
% DELTA Parameter for the precision check (optional; default: 1e-12)
%
% OUTPUT
% OK 1 if the matrix A is symmetric and 0, otherwise.
%
% DESCRIPTION
% A is considered as a symmetric matrix, when it is square and
% max(max(A-A')) is smaller than DELTA.
%
%
% Robert P.W. Duin, Elzbieta Pekalska, ela@ph.tn.tudelft.nl
% Faculty of Applied Sciences, Delft University of Technology
%
function [ok,nn] = issym(A,delta)
if nargin < 2,
prwarning(6,'The precision is not provided, set up to 1e-12.');
delta = 1e-12;
end
A = +A;
[m,k] = size(A);
if m ~= k,
error ('Matrix should be square.')
end
nn = max(max((A-A')));
ok = (nn < delta);
return;