How do I handle datasets with an excess number of zero counts?

For data with an excess of zeros, you can use a zero-inflated model by setting the 'modeltype' parameter to 'ZIP', 'ZINB', or 'ZICMPOISSON'. You must also specify the regressors for the zero-inflation component of the model using the 'zeromodel' parameter. The link function for this part can be set to 'LOGISTIC' (the default) or 'NORMAL'.