void ZIGM::check_log_probabilities() const {
if (log_probabilities_are_current_) return;
log_probability_of_positive_ = log(positive_probability());
log_probability_of_zero_ = log(1 - positive_probability());
log_probabilities_are_current_ = true;
}
double ZIGM::variance() const {
double p = positive_probability();
return p * square(mean_parameter()) * (1 - p + (1 / shape_parameter()));
}
double ZIGM::sim(RNG &rng) const {
if (runif_mt(rng) < positive_probability()) {
return gamma_->sim(rng);
}
return 0;
}
double ZIGM::mean() const {
return positive_probability() * mean_parameter();
}
double ZIGM::sim()const{
if(runif() < positive_probability()){
return gamma_->sim();
}
return 0;
}
