code 41550;
real procedure LOGISTIC(X, MU, SIGMA);
value X, MU, SIGMA; real X, MU, SIGMA;
LOGISTIC:= if SIGMA ≤ 0
           then STATAL3 ERROR(“LOGISTIC”, 3, SIGMA)
           else 1 / (1 + EXP(-(X - MU) / SIGMA));
eop