mcmc.PlotTrackingCum throws error for Pareto/NBD (Abe)

[mplatzer]

(bug report thanks to Keith Botner)

cdnowElog <- read.csv(system.file("data/cdnowElog.csv", package = "BTYD"),
                      stringsAsFactors = FALSE,
                      col.names = c("cust", "sampleid", "date", "cds", "sales"))

cdnowElog$date <- as.Date(as.character(cdnowElog$date), format = "%Y%m%d")
cbs <- elog2cbs(cdnowElog, T.cal = "1997-09-30", T.tot = "1998-06-30")

first <- aggregate(sales ~ cust, cdnowElog, function(x) x[1] * 10^-3)
names(first) <- c("cust", "first.sales")

cbs <- merge(cbs, first, by = "cust")

draws.m2 <- abe.mcmc.DrawParameters(cbs,
                                    covariates = c("first.sales"),
                                    mcmc = 7500, burnin = 2500)
weekly_cum_repeat <- elog2cum(cdnowElog)
cum_vs_exp_repeat <- mcmc.PlotTrackingCum(draws.m2,
                                          T.cal = cbs$T.cal,
                                          T.tot = round(max(cbs$T.cal + cbs$T.star)),
                                          weekly_cum_repeat,
                                          sample_size = 10000)

throws

Error in covars %*% params$beta : 
  requires numeric/complex matrix/vector arguments