Calculate the log-likelihood of the MBG/NBD model
mbgnbd.LL(params, x, t.x, T.cal)MBG/NBD parameters - a vector with r, alpha, a
and b in that order.
frequency, i.e. number of re-purchases
recency, i.e. time elapsed from first purchase to last purchase
total time of observation period
a vector of log-likelihoods
Batislam, E.P., M. Denizel, A. Filiztekin. 2007. Empirical validation and comparison of models for customer base analysis. International Journal of Research in Marketing 24(3) 201-209. - Hoppe, Daniel, and Udo Wagner. 'Customer base analysis: The case for a central variant of the Betageometric/NBD Model.' Marketing Journal of Research and Management 3.2 (2007): 75-90.