function retval = mu(t)
% usage: y = mu(t);
% description: Returns value of mu or mu' at scalar t.

global mindex; % will give 0th or 1th derivative of mu
global malpha; % a parameter for mu

if (mindex == 0)
%  retval = (1-exp(-malpha*t))/malpha; % example 1,2
  retval = t^2; % example 3
else
%  retval = exp(-malpha*t); % example 1,2
  retval = 2*t; % example 3
end;