function[X]=logistic(b,tvec,yvec)

%  X(X0,M,k,t) = M*X0*exp(kt) / ((M-X0)+X0*exp(kt))  (a)
%              = M*X0 / (X0+(M-X0)exp(-kt))         (b)
%

X0 = b(1);
M = b(2);
k = b(3);

X = X0*M./((M-X0)*exp(-k*tvec)+X0);