function F = exp_cdf(X,muX)
% F = exp_cdf(X,muX)
% return CDF of exponential distribution with mean muX , at points X
%
%    Reference: http://en.wikipedia.org/wiki/Exponential_distribution

  idx = find(X<=0);
  X(idx) = 0.01;

  F = 1.0 -  exp(-X/muX); 

% ----------------------------------------------------------------- exp_cdf
