pnbd.ExpectedCumulativeTransactions: Pareto/NBD Expected Cumulative Transactions

Description

Calculates the expected cumulative total repeat transactions by all customers for the calibration and holdout periods.

Usage

pnbd.ExpectedCumulativeTransactions(params, T.cal, T.tot, n.periods.final)

Arguments

params

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.

T.cal

a vector to represent customers' calibration period lengths (in other words, the "T.cal" column from a customer-by-sufficient-statistic matrix).

T.tot

end of holdout period. Must be a single value, not a vector.

n.periods.final

number of time periods in the calibration and holdout periods. See details.

Value

Vector of expected cumulative total repeat transactions by all customers.

Details

The function automatically divides the total period up into n.periods.final time intervals. n.periods.final does not have to be in the same unit of time as the T.cal data. For example:

- if your T.cal data is in weeks, and you want cumulative transactions per week, n.periods.final would equal T.star.

- if your T.cal data is in weeks, and you want cumulative transactions per day, n.periods.final would equal T.star * 7.

The holdout period should immediately follow the calibration period. This function assume that all customers' calibration periods end on the same date, rather than starting on the same date (thus customers' birth periods are determined using max(T.cal) - T.cal rather than assuming that it is 0).

Examples

Run this code

data(cdnowSummary)

cal.cbs <- cdnowSummary$cbs
# cal.cbs already has column names required by method

params <- c(0.55, 10.56, 0.61, 11.64)

# Returns a vector containing cumulative repeat transactions for 546 days.
# All parameters are in weeks; the calibration period lasted 39 weeks
# and the holdout period another 39.
pnbd.ExpectedCumulativeTransactions(params, T.cal=cal.cbs[,"T.cal"],
	T.tot=78, n.periods.final=546)