Calibration period CBS. It must contain columns for frequency
x and total time observed T.cal.
par.start
Initial NBD parameters - a vector with r and alpha in
that order.
max.param.value
Upper bound on parameters.
Value
List of estimated parameters.
References
Ehrenberg, A. S. (1959). The pattern of consumer purchases.
Journal of the Royal Statistical Society: Series C (Applied Statistics),
8(1), 26-41. 10.2307/2985810