zero-inflated models

Tweedie models are a special Generalized Linear Model (GLM) that can be useful when we want to model an outcome that sometimes equals 0 but is otherwise positive and continuous. Some examples include daily precipitation data and annual income. Data like this can have zeroes, often lots of zeroes, in addition to positive values. When modeling data of this nature, we may want to ensure our model does not predict negative values. We may also want to log-transform this data without dropping the zeroes. Tweedie models allow us to do both.

A count model is a linear model where the dependent variable is a count. For example, the number of times a car breaks down, the number of rats in a litter, the number of times a young student gets out of his seat, etc. Counts are either 0 or a positive whole number, which means we need to use special distributions to generate the data.