Pareto/NBD parameters - a vector with r, alpha, s, and beta, in
that order. r and alpha are unobserved parameters for the NBD transaction
process. s and beta are unobserved parameters for the Pareto (exponential
gamma) dropout process.
lim
The upper-bound of the x-axis. A number is chosen by the function
if none is provided.
Value
Distribution of customers' propensities to purchase.
Details
This returns the distribution of each customer's Poisson parameter, which
determines the level of their purchasing (using the Pareto/NBD assumption
that purchasing on the individual level can be modeled with a Poisson
distribution).