mdp_check_square_stochastic( Z )

function error_msg = mdp_check_square_stochastic( Z )


% mdp_check_square_stochastic     Check if Z is a square stochastic matrix
% Arguments ---------------------------------------------------------------
%   Z(SxS) = a matrix
% Evaluation --------------------------------------------------------------
%   error_msg = error message or '' if correct

% MDPtoolbox: Markov Decision Processes Toolbox
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error_msg = '';

[s1 s2] = size(Z);
if s1 ~=s2
   error_msg = 'MDP Toolbox ERROR: Matrix must be square';
elseif max(abs(sum(Z,2)-ones(s2,1))) > 10^(-12)
   error_msg = 'MDP Toolbox ERROR: Row sums of the matrix must be 1';
elseif ~isempty(find (Z < 0))
   error_msg = 'MDP Toolbox ERROR: Probabilities must be non-negative';
end;