Calculate the log-likelihood of the NBD model
nbd.cbs.LL(params, cal.cbs)NBD parameters - a vector with r and alpha, in that order.
calibration period CBS. It must contain columns for frequency
x and total time observed T.cal. Optionally a column custs can be
provided, which represents number of customers with a specific combination
of frequency x and T.cal data.frame with columns x and T.cal and
optional custs.
the total log-likelihood for the provided data.